Money Market Funds · Shareholder fees (fees paid directly from your investment) Maximum front-end sales charge (load) imposed on purchases None Maximum deferred sales charge (load)

Money Market FundsProspectus | December 30, 2019

Includes:• UBS Select Prime Preferred Fund: SPPXX• UBS Select Government Preferred Fund: SGPXX• UBS Select Treasury Preferred Fund: STPXX• UBS Select ESG Prime Preferred Fund: SSPXX

As with all mutual funds, the Securities and Exchange Commission has not approved or disapproved thefunds’ shares or determined whether this prospectus is complete or accurate. To state otherwise is acrime.

Not FDIC Insured. May lose value. No bank guarantee.

ContentsThe fundsWhat every investor should know about the funds

Fund summariesUBS Select Prime Preferred Fund 3UBS Select Government Preferred Fund 9UBS Select Treasury Preferred Fund 14UBS Select ESG Prime Preferred Fund 20

More information about the funds 26

Your investmentInformation for managing your fund accountManaging your fund account 34—Buying shares—Selling shares—Exchanging shares—Transfer of account limitations—Additional information about your account—Market timing—Pricing and valuation

Additional informationAdditional important information about the fundsManagement 48Dividends and taxes 49Disclosure of portfolio holdings and other information 51Financial highlights 53Appendix A: Additional information regarding purchases and redemptions 57Where to learn more about the funds Back cover

Please find the UBS family of funds privacy notice on page 58. Please find the UBS AssetManagement business continuity planning overview on page 60.

The funds are not a complete or balanced investment program.

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UBS Select Prime Preferred FundFund summary

Investment objectiveMaximum current income consistent with liquidity and the preservation of capital.

Fees and expenses of the fundThese tables describe the fees and expenses that you may pay if you buy and hold shares of the fund.

Shareholder fees (fees paid directly from your investment)

Maximum front-end sales charge (load) imposed on purchases None

Maximum deferred sales charge (load) None

Annual fund operating expenses (expenses that you pay each year as a percentage of the value ofyour investment)*

Management fees 0.18%

Distribution and/or service (12b-1) fees None

Other expenses** None

Total annual fund operating expenses 0.18

Fee waiver1 0.04

Total annual fund operating expenses after fee waiver1 0.14

* The fund invests in securities through an underlying master fund, Prime Master Fund. This table reflects the direct expenses of the fund and its share ofexpenses of Prime Master Fund, including management fees allocated from Prime Master Fund. Management fees are comprised of investment advisoryand administration fees.

** “Other expenses” do not include miscellaneous expenses, such as trustee expenses, for which UBS Asset Management (Americas) Inc. (“UBS AM”)reimburses the fund. These other expenses are expected to be less than 0.01% of the average daily net assets of the fund.

1 The fund and UBS AM have entered into a written fee waiver agreement pursuant to which UBS AM is contractually obligated to waive its managementfees so that the total ordinary operating expenses of the fund through December 31, 2020, do not exceed 0.14%. The fee waiver agreement may beterminated by the fund’s board at any time and also will terminate automatically upon the expiration or termination of the fund’s contract with UBS AM.

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ExampleThis example is intended to help you compare the cost of investing in the fund with the cost of investing inother mutual funds. The example assumes that you invest $10,000 in the fund for the time periods indi-cated and then redeem all of your shares at the end of those periods. The example also assumes that yourinvestment has a 5% return each year and that the fund’s operating expenses remain the same.*

Although your actual costs may be higher or lower, based on these assumptions your costs would be:

1 year 3 years 5 years 10 years

UBS Select Prime Preferred Fund $14 $54 $97 $226

* Except that the expenses reflect the effects of the fund’s fee waiver agreement for the first year only.

Principal strategiesPrincipal investmentsThe fund is a money market fund that calculates its net asset value to four decimals (e.g., $1.0000) usingmarket-based pricing. As a result, its share price will fluctuate. The fund seeks to achieve its objective byinvesting in a diversified portfolio of high quality money market instruments of governmental and privateissuers. These may include:

• short-term obligations of the US government and its agencies and instrumentalities;• repurchase agreements;• obligations of issuers in the financial services group of industries;• commercial paper, other corporate obligations and asset-backed securities; and• municipal money market instruments.

Money market instruments generally are short-term debt obligations and similar securities. They also mayinclude longer-term bonds that have variable interest rates or other special features that give them thefinancial characteristics of short-term debt. The fund invests in foreign money market instruments only ifthey are denominated in US dollars. The fund will, under normal circumstances, invest more than 25% ofits total assets in the financial services group of industries.

The fund invests in securities through an underlying master fund. The fund and its corresponding masterfund have the same objective. Unless otherwise indicated, references to the fund include the master fund.

The fund may be subject to the possible imposition of a liquidity fee and/or temporary redemption gateshould certain triggering events occur.

Management processUBS AM acts as the investment advisor. As investment advisor, UBS AM makes the fund’s investment deci-sions. UBS AM selects money market instruments for the fund based on its assessment of relative valuesand changes in market and economic conditions.

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UBS AM considers safety of principal and liquidity in selecting securities for the fund and thus may not buysecurities that pay the highest yield.

Principal risksAll investments carry a certain amount of risk, and the fund cannot guarantee that it will achieve its invest-ment objective.

You could lose money by investing in the fund. Because the share price of the fund will fluctuate, whenyou sell your shares they may be worth more or less than what you originally paid for them. Also, the fundmay impose a fee upon the sale of your shares or may temporarily suspend your ability to sell shares if thefund’s liquidity falls below required minimums because of market conditions or other factors. An invest-ment in the fund is not insured or guaranteed by the Federal Deposit Insurance Corporation or any othergovernment agency. The fund’s sponsor has no legal obligation to provide financial support to the fund,and you should not expect that the sponsor will provide financial support to the fund at any time.

Money market instruments generally have a low risk of loss, but they are not risk-free. The principal riskspresented by an investment in the fund are:

Credit risk: Issuers of money market instruments or financial institutions that have entered into repur-chase agreements with the fund may fail to make payments when due or complete transactions, or theymay become less willing or less able to do so.

Interest rate risk: The value of the fund’s investments generally will fall when interest rates rise, and itsyield will tend to lag behind prevailing rates. The fund may face a heightened level of interest rate risk dueto certain changes in monetary policy, such as certain types of interest rate changes by the FederalReserve.

Market risk: The risk that the market value of the fund’s investments may fluctuate, sometimes rapidly orunpredictably, as the markets fluctuate, which may affect the fund’s share price. Market risk may affect asingle issuer, industry, or sector of the economy, or it may affect the market as a whole. Moreover, chang-ing market, economic, political and social conditions in one country or geographic region could adverselyimpact market, economic, political and social conditions in other countries or regions.

Liquidity risk: Although the fund invests in a diversified portfolio of high quality instruments, the fund’sinvestments may become less liquid as a result of market developments or adverse investor perception.

Management risk: The risk that the investment strategies, techniques and risk analyses employed by theadvisor may not produce the desired results.

Concentration risk: The fund will invest a significant portion of its assets in securities issued by compa-nies in the financial services group of industries, including US banking, non-US banking, broker-dealers,

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insurance companies, finance companies (e.g., automobile finance) and related asset-backed securities.Accordingly, the fund will be more susceptible to developments that affect those industries than otherfunds that do not concentrate their investments.

Financial services sector risk: Investments of the fund in the financial services sector may be particularlyaffected by economic cycles, business developments, interest rate changes and regulatory changes.

US Government securities risk: There are different types of US government securities with different levelsof credit risk, including the risk of default, depending on the nature of the particular government support forthat security. For example, a US government-sponsored entity, such as Federal National Mortgage Associa-tion (“Fannie Mae”) or Federal Home Loan Mortgage Corporation (“Freddie Mac”), although chartered orsponsored by an Act of Congress, may issue securities that are neither insured nor guaranteed by the USTreasury and are therefore riskier than those that are.

Foreign investing risk: The value of the fund’s investments in foreign securities may fall due to adversepolitical, social and economic developments abroad. However, because the fund’s foreign investmentsmust be denominated in US dollars, it generally is not subject to the risk of changes in currency valuations.

Municipal securities risk: Municipal securities are subject to interest rate and credit risks. The ability of amunicipal issuer to make payments and the value of municipal securities can be affected by uncertaintiesin the municipal securities market. Such uncertainties could cause increased volatility in the municipal secu-rities market and could negatively impact the fund’s net asset value and/or the distributions paid by thefund. Municipalities continue to experience difficulties in the current economic and political environment.

PerformanceRisk/return bar chart and tableThe following bar chart and table provide information about the fund’s performance and thus give someindication of the risks of an investment in the fund.

The bar chart shows how the fund’s performance has varied from year to year.

The table that follows the bar chart shows the average annual returns over the various time periods for thefund’s shares.

The fund’s past performance does not necessarily indicate how the fund will perform in the future.

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UBS Select Prime Preferred Fund Annual Total ReturnsTotal return

0

1

2

3

4%

Calendar Year

0.49%

2009

0.19%

2010

0.17%

2011

0.18%

2012

0.09%

2013

0.06%

2014 2017

0.12%

2015

0.52%

2016

1.14%

2.01%

2018

Total return January 1 to September 30, 2019: 1.80%Best quarter during years shown—4Q 2018: 0.58%Worst quarter during years shown—1Q 2014: 0.01%

Updated performance information is available (1) by contacting your Financial Advisor, (2) by calling1-888-793 8637 (Option #1) and (3) on the fund’s website athttps://www.ubs.com/usmoneymarketfunds.

Average annual total returns (for the periods ended December 31, 2018)

One year 2.01%

Five years 0.77

Ten years 0.49

Investment advisorUBS AM serves as the investment advisor to the fund.

Purchase & sale of fund sharesIf you are buying or selling fund shares directly, you may do so by calling the fund’s transfer agent at1-888-547 FUND. You may also buy and sell fund shares through financial intermediaries who are autho-rized to accept purchase and sales orders on behalf of the fund. This includes the ability to buy fund sharesthrough a UBS Financial Services Inc. Financial Advisor using that firm’s automated order entry system. Theminimum investment level for initial purchases generally is $99,000,000. Subsequent purchases, and pur-chases through exchanges, are not subject to a minimum investment level. Shares of the fund may beredeemed in the same manner as they were purchased (i.e., directly or through a financial intermediary,including through UBS Financial Services Inc.’s automated order entry system). Shares can be purchased

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and redeemed on any business day on which the Federal Reserve Bank of New York, the New York StockExchange and the principal bond markets (as recommended by the Securities Industry and Financial Mar-kets Association) are open (unless a liquidity fee and/or temporary redemption gate has been imposedunder exceptional circumstances).

Tax informationThe dividends and distributions you receive from the fund are taxable and will generally be taxed as ordi-nary income, capital gains or some combination of both, unless you hold shares through a tax-exemptaccount or plan, such as an individual retirement account or 401(k) plan, in which case dividends and dis-tributions on your shares generally will be taxed when withdrawn from the tax-exempt account or plan.

Payments to broker-dealers and other financial intermediariesIf you purchase the fund through a broker-dealer or other financial intermediary (such as a bank), UBS AMand/or its affiliates may pay the intermediary for the sale of fund shares and related services, or othershareholder services. These payments may create a conflict of interest by influencing the broker-dealer orother intermediary and your financial advisor to recommend the fund over another investment. Ask yourfinancial advisor or visit your financial intermediary’s website for more information.

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UBS Select Government Preferred FundFund summary











Fee waiver1 0.04


* The fund invests in securities through an underlying master fund, Government Master Fund. This table reflects the direct expenses of the fund and itsshare of expenses of Government Master Fund, including management fees allocated from Government Master Fund. Management fees are comprisedof investment advisory and administration fees.



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UBS Select Government Preferred Fund $14 $54 $97 $226


Principal strategiesPrincipal investmentsThe fund is a money market fund and seeks to maintain a stable price of $1.00 per share. To do this, thefund invests in a diversified portfolio of high quality, US government money market instruments and inrelated repurchase agreements.

Money market instruments generally are short-term debt obligations and similar securities. They also mayinclude longer-term bonds that have variable interest rates or other special features that give them thefinancial characteristics of short-term debt. The fund has adopted a policy to invest 99.5% or more of itstotal assets in cash, government securities, and/or repurchase agreements that are collateralized fully (i.e.,collateralized by cash and/or government securities) in order to qualify as a “government money marketfund” under federal regulations. By operating as a government money market fund, the fund is exemptfrom requirements that permit the imposition of a liquidity fee and/or temporary redemption gates. Whilethe fund’s board may elect to subject the fund to liquidity fee and gate requirements in the future, theboard has not elected to do so at this time. Many US government money market instruments pay incomethat is generally exempt from state and local income tax, although they may be subject to corporate fran-chise tax in some states. In addition, under normal circumstances, the fund invests at least 80% of its netassets in US government securities, including government securities subject to repurchase agreements.

The fund may invest a significant percentage of its assets in repurchase agreements. Repurchase agree-ments are transactions in which the fund purchases government securities and simultaneously commits toresell them to the same counterparty at a future time and at a price reflecting a market rate of interest.Income from repurchase agreements may not be exempt from state and local income taxation. Repur-chase agreements often offer a higher yield than investments directly in government securities. In decidingwhether an investment in a repurchase agreement is more attractive than a direct investment in govern-ment securities, the fund considers the possible loss of this tax advantage.


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You could lose money by investing in the fund. Although the fund seeks to preserve the value of yourinvestment at $1.00 per share, it cannot guarantee it will do so. An investment in the fund is not insuredor guaranteed by the Federal Deposit Insurance Corporation or any other government agency. The fund’ssponsor has no legal obligation to provide financial support to the fund, and you should not expect thatthe sponsor will provide financial support to the fund at any time.



Interest rate risk: The value of the fund’s investments generally will fall when interest rates rise, and itsyield will tend to lag behind prevailing rates. The fund may face a heightened level of interest rate risk dueto certain changes in monetary policy, such as certain types of interest rate changes by the FederalReserve.

US Government securities risk: There are different types of US government securities with different lev-els of credit risk, including the risk of default, depending on the nature of the particular government sup-port for that security. For example, a US government-sponsored entity, such as Federal National MortgageAssociation (“Fannie Mae”) or Federal Home Loan Mortgage Corporation (“Freddie Mac”), although char-tered or sponsored by an Act of Congress, may issue securities that are neither insured nor guaranteed bythe US Treasury and are therefore riskier than those that are.


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The table that follows the bar chart shows the average annual returns over various time periods for thefund’s shares.


UBS Select Government Preferred Fund Annual Total ReturnTotal return (2017 was the fund’s first full calendar year of operations)

0

1

2

3%

2017 2018

0.78%

Calendar Year

1.73%

Total return January 1 to September 30, 2019: 1.69%Best quarter during years shown—4Q 2018: 0.53%Worst quarter during years shown—1Q 2017: 0.13%

Updated performance information is available (1) by contacting your Financial Advisor, (2) by calling1-888-793 8637 (Option #1) and (3) on the fund’s website at https://www.ubs.com/usmoneymarketfunds.

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One year 1.73%

Life of fund (inception date June 28, 2016) 1.06


Purchase & sale of fund sharesIf you are buying or selling fund shares directly, you may do so by calling the fund’s transfer agent at1-888-547 FUND. You may also buy and sell fund shares through financial intermediaries who are autho-rized to accept purchase and sales orders on behalf of the fund. This includes the ability to buy fund sharesthrough a UBS Financial Services Inc. Financial Advisor using that firm’s automated order entry system. Theminimum investment level for initial purchases generally is $50,000,000. Subsequent purchases, and pur-chases through exchanges, are not subject to a minimum investment level. Shares of the fund may beredeemed in the same manner as they were purchased (i.e., directly or through a financial intermediary,including through UBS Financial Services Inc.’s automated order entry system). Shares can be purchasedand redeemed on any business day on which the Federal Reserve Bank of New York, the New York StockExchange and the principal bond markets (as recommended by the Securities Industry and Financial Mar-kets Association) are open.



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UBS Select Treasury Preferred FundFund summary











Fee waiver1 0.04


* The fund invests in securities through an underlying master fund, Treasury Master Fund. This table reflects the direct expenses of the fund and its shareof expenses of Treasury Master Fund, including management fees allocated from Treasury Master Fund. Management fees are comprised of investmentadvisory and administration fees.



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UBS Select Treasury Preferred Fund $14 $54 $97 $226


Principal strategiesPrincipal investmentsThe fund is a money market fund and seeks to maintain a stable price of $1.00 per share. To do this,under normal circumstances, the fund invests in a diversified portfolio of high quality, US Treasury moneymarket instruments and in related repurchase agreements.

Money market instruments generally are short-term debt obligations and similar securities. They also mayinclude longer-term bonds that have variable interest rates or other special features that give them thefinancial characteristics of short-term debt. The fund has adopted a policy to invest 99.5% or more of itstotal assets in cash, government securities, and/or repurchase agreements that are collateralized fully (i.e.,collateralized by cash and/or government securities) in order to qualify as a “government money marketfund” under federal regulations. By operating as a government money market fund, the fund is exemptfrom requirements that permit the imposition of a liquidity fee and/or temporary redemption gates. Whilethe fund’s board may elect to subject the fund to liquidity fee and gate requirements in the future, theboard has not elected to do so at this time. In addition, in order to be a “Treasury” fund, under normalcircumstances, the fund seeks to achieve its objective by investing at least 80% of its net assets (plus theamount of any borrowing for investment purposes) in securities issued by the US Treasury and in relatedrepurchase agreements. For purposes of this policy, repurchase agreements are those that are collateral-ized fully by securities issued by the US Treasury and cash. Under normal circumstances, the fund expectsto invest substantially all of its assets in securities issued by the US Treasury and in related repurchaseagreements. Many US government money market instruments pay income that is generally exempt fromstate and local income tax, although they may be subject to corporate franchise tax in some states.

The fund may invest a significant percentage of its assets in repurchase agreements. Repurchase agree-ments are transactions in which the fund purchases securities issued by the US Treasury and simultane-ously commits to resell them to the same counterparty at a future time and at a price reflecting a marketrate of interest. Income from repurchase agreements may not be exempt from state and local income tax-ation. Repurchase agreements often offer a higher yield than investments directly in securities issued by

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the US Treasury. In deciding whether an investment in a repurchase agreement is more attractive than adirect investment in securities issued by the US Treasury, the fund considers the possible loss of this taxadvantage.

Money market instruments generally are short-term debt obligations and similar securities. They also mayinclude longer-term bonds that have variable interest rates or other special features that give them thefinancial characteristics of short-term debt.





You could lose money by investing in the fund. Although the fund seeks to preserve the value of yourinvestment at $1.00 per share, it cannot guarantee it will do so. An investment in the fund is not insuredor guaranteed by the Federal Deposit Insurance Corporation or any other government agency. The fund’ssponsor has no legal obligation to provide financial support to the fund, and you should not expect thatthe sponsor will provide financial support to the fund at any time.



Interest rate risk: The value of the fund’s investments generally will fall when interest rates rise, and its yieldwill tend to lag behind prevailing rates. The fund may face a heightened level of interest rate risk due to cer-tain changes in monetary policy, such as certain types of interest rate changes by the Federal Reserve.

16

US Government securities risk: There are different types of US government securities with different lev-els of credit risk, including the risk of default, depending on the nature of the particular government sup-port for that security. For example, a US government-sponsored entity, such as Federal National MortgageAssociation (“Fannie Mae”) or Federal Home Loan Mortgage Corporation (“Freddie Mac”), although char-tered or sponsored by an Act of Congress, may issue securities that are neither insured nor guaranteed bythe US Treasury and are therefore riskier than those that are.






The table that follows the bar chart shows the average annual returns over the various time periods for thefund’s shares.


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UBS Select Treasury Preferred Fund Annual Total ReturnsTotal return

0

1

2

3

4%

Calendar Year

0.13%

2009

0.06%

2010

0.01%

2011

0.02%

2012 2013

0.01%

2017

0.02%

20152014

0.01% 0.22%

2016

0.76%

2018

1.74%

Total return January 1 to September 30, 2019: 1.68%Best quarter during years shown—4Q 2018: 0.54%Worst quarters during years shown—1Q 2014; 1Q 2015: 0.00% (Actual total returns were 0.0025%)

Updated performance information is available (1) by contacting your Financial Advisor, (2) by calling1-888-793 8637 (Option #1) and (3) on the fund’s website at https://www.ubs.com/usmoneymarketfunds.


One year 1.74%

Five years 0.55

Ten years 0.30


Purchase & sale of fund sharesIf you are buying or selling fund shares directly, you may do so by calling the fund’s transfer agent at1-888-547 FUND. You may also buy and sell fund shares through financial intermediaries who are autho-rized to accept purchase and sales orders on behalf of the fund. This includes the ability to buy fund sharesthrough a UBS Financial Services Inc. Financial Advisor using that firm’s automated order entry system. Theminimum investment level for initial purchases generally is $50,000,000. Subsequent purchases, and pur-chases through exchanges, are not subject to a minimum investment level. Shares of the fund may beredeemed in the same manner as they were purchased (i.e., directly or through a financial intermediary,including through UBS Financial Services Inc.’s automated order entry system). Shares can be purchasedand redeemed on any business day on which the Federal Reserve Bank of New York, the New York Stock

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Exchange and the principal bond markets (as recommended by the Securities Industry and Financial Mar-kets Association) are open.



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UBS Select ESG Prime Preferred FundFund summary

Investment objectiveMaximum current income as is consistent with liquidity and preservation of capital while incorporatingselect environmental, social, and governance criteria (“ESG”) into the investment process.










Fee waiver1 0.04


* The fund invests in securities through an underlying master fund, ESG Prime Master Fund. This table reflects the direct expenses of the fund and itsshare of expenses of ESG Prime Master Fund, including management fees allocated from ESG Prime Master Fund. Management fees are comprised ofinvestment advisory and administration fees.



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1 year 3 years

UBS Select ESG Prime Preferred Fund $14 $54


Principal strategiesPrincipal investmentsThe fund is a money market fund that calculates its net asset value to four decimals (e.g., $1.0000) usingmarket-based pricing. As a result, its share price will fluctuate. The fund seeks to achieve its objective byinvesting in a diversified portfolio of high quality money market instruments of governmental and privateissuers while incorporating fundamental sustainability factors, such as ESG performance of such issuers,into the investment process. Money market instruments may include:

• short-term obligations of the US government and its agencies and instrumentalities;• repurchase agreements;• obligations of issuers in the financial services group of industries;• commercial paper, other corporate obligations and asset-backed securities; and• municipal money market instruments.

Money market instruments generally are short-term debt obligations and similar securities. They also mayinclude longer-term bonds that have variable interest rates or other special features that give them thefinancial characteristics of short-term debt. The fund invests in foreign money market instruments only ifthey are denominated in US dollars. The fund will, under normal circumstances, invest more than 25% ofits total assets in the financial services group of industries.

In addition, under normal circumstances, the fund invests at least 80% of its net assets (plus the amountof any borrowing for investment purposes), determined at the time of purchase, in securities that meetUBS AM’s sustainability criteria. In developing its sustainability criteria, UBS AM draws upon firm-wideresources of the UBS Asset Management Division of UBS Group AG, of which UBS AM is a member.

UBS AM conducts its own credit analyses of potential investments and portfolio holdings, and relies sub-stantially on a dedicated proprietary credit research team. Embedded in the credit research process is theintegration of issuer-level sustainability investing analysis as guided by the UBS Asset Management Divi-sion’s approach to ESG research and evaluation methodology. The sustainability investing analysis providesa more comprehensive approach to security selection than credit analysis alone as internal and external

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ESG ratings are applied to evaluate the quality of sustainability practices employed by issuers. Analysts rateand maintain internal fundamental credit and ESG ratings, which form the basis for a portfolio construc-tion/optimization approach and focus on issuers that contribute to the fund’s ESG profile. In determiningan issuer’s ESG ratings, analysts will evaluate whether, at the time of the fund’s investment, such issuershave better than average performance in ESG practices and managing ESG risks by reviewing, amongother factors, such considerations as the issuer’s environmental responsibility, human rights and laborstandards, diversity and inclusion in employment and corporate governance based on proprietary andthird-party data. UBS AM also will employ a negative screening process with regard to security selection,which will exclude from the fund’s portfolio securities or sectors that manufacture products or engage inbusiness activities viewed as having a negative social or environmental impact. UBS AM’s portfolio con-struction process aims to align investments in money market instruments with the concept of sustainability(i.e., the potential for long-term maintenance of environmental, economic and social well-being).


The fund may be subject to the possible imposition of a liquidity fee and/or temporary redemption gateshould certain triggering events occur.



UBS AM is part of the UBS Asset Management Division of UBS Group AG. The UBS Asset ManagementDivision, at the global level, seeks to be a leader in incorporating sustainability into its management pro-cess and honors various commitments in the sustainability investing industry. Active commitments include:

• Participant in the UN Global Compact since its inception in 2000• Independent assurance of the GRI (Global Reporting Initiative) based sustainability disclosure• UBS Asset Management signatory to Principles for Responsible Investment (PRI)• Global Initiative for Sustainability Ratings steering committee• Sustainability Accounting Standards BoardTM

• The Forum for Sustainable and Responsible Investing


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You could lose money by investing in the fund. Because the share price of the fund will fluctuate, whenyou sell your shares they may be worth more or less than what you originally paid for them. Also, the fundmay impose a fee upon the sale of your shares or may temporarily suspend your ability to sell shares if thefund’s liquidity falls below required minimums because of market conditions or other factors. An invest-ment in the fund is not insured or guaranteed by the Federal Deposit Insurance Corporation or any othergovernment agency. The fund’s sponsor has no legal obligation to provide financial support to the fund,and you should not expect that the sponsor will provide financial support to the fund at any time.



Interest rate risk: The value of the fund’s investments generally will fall when interest rates rise, and its yieldwill tend to lag behind prevailing rates. The fund may face a heightened level of interest rate risk due to cer-tain changes in monetary policy, such as certain types of interest rate changes by the Federal Reserve.

Sustainability factor risk: Investing primarily in investments that meet ESG criteria carries the risk thatthe fund may forgo otherwise attractive investment opportunities, or increase or decrease its exposure tocertain types of issuers and, therefore, may underperform compared to funds that do not consider ESGfactors in the investment process.




Concentration risk: The fund will invest a significant portion of its assets in securities issued by compa-nies in the financial services group of industries, including US banking, non-US banking, broker-dealers,insurance companies, finance companies (e.g., automobile finance) and related asset-backed securities.Accordingly, the fund will be more susceptible to developments that affect those industries than otherfunds that do not concentrate their investments.

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Financial services sector risk: Investments of the fund in the financial services sector may be particularlyaffected by economic cycles, business developments, interest rate changes and regulatory changes.

US Government securities risk: There are different types of US government securities with different lev-els of credit risk, including the risk of default, depending on the nature of the particular government sup-port for that security. For example, a US government-sponsored entity, such as Federal National MortgageAssociation (“Fannie Mae”) or Federal Home Loan Mortgage Corporation (“Freddie Mac”), althoughchartered or sponsored by an Act of Congress, may issue securities that are neither insured nor guaran-teed by the US Treasury and are therefore riskier than those that are.

Foreign investing risk: The value of the fund’s investments in foreign securities may fall due to adversepolitical, social and economic developments abroad. However, because the fund’s foreign investmentsmust be denominated in US dollars, it generally is not subject to the risk of changes in currency valuations.

Municipal securities risk: Municipal securities are subject to interest rate and credit risks. The ability of amunicipal issuer to make payments and the value of municipal securities can be affected by uncertaintiesin the municipal securities market. Such uncertainties could cause increased volatility in the municipal secu-rities market and could negatively impact the fund’s net asset value and/or the distributions paid by thefund. Municipalities continue to experience difficulties in the current economic and political environment.

New fund risk: The fund is new with no operating history. As a result, prospective investors have no trackrecord or history on which to base their investment decisions.

PerformanceThere is no performance information quoted for the fund as the fund had not commenced investmentoperations as of the date of this prospectus.


Purchase & sale of fund sharesIf you are buying or selling fund shares directly, you may do so by calling the fund’s transfer agent at1-888-547 FUND. You may also buy and sell fund shares through financial intermediaries who are autho-rized to accept purchase and sales orders on behalf of the fund. This includes the ability to buy fund sharesthrough a UBS Financial Services Inc. Financial Advisor using that firm’s automated order entry system. Theminimum investment level for initial purchases generally is $99,000,000. Subsequent purchases, and pur-chases through exchanges, are not subject to a minimum investment level. Shares of the fund may beredeemed in the same manner as they were purchased (i.e., directly or through a financial intermediary,including through UBS Financial Services Inc.’s automated order entry system). Shares can be purchasedand redeemed on any business day on which the Federal Reserve Bank of New York, the New York StockExchange and the principal bond markets (as recommended by the Securities Industry and Financial Mar-kets Association) are open (unless a liquidity fee and/or temporary redemption gate has been imposedunder exceptional circumstances).

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UBS Series Funds

More information about the funds

Additional information about the investmentobjectivesEach of UBS Select Prime Preferred Fund’s, UBSSelect Government Preferred Fund’s and UBS SelectTreasury Preferred Fund’s investment objective maynot be changed without shareholder approval. Theinvestment objective of UBS Select ESG Prime Pre-ferred Fund is non-fundamental and may bechanged by the fund’s board at any time withoutshareholder approval.

Additional information about investmentstrategiesUBS Select Prime Preferred Fund seeks to achieve itsinvestment objective by investing in a diversifiedportfolio of high quality money market instrumentsof governmental and private issuers, which mayinclude short-term obligations of the US govern-ment and its instrumentalities; repurchase agree-ments; obligations of issuers in the financial servicesgroup of industries; commercial paper, other corpo-rate obligations and asset-backed securities; andmunicipal money market instruments.

UBS Select Prime Preferred Fund calculates its net assetvalue to four decimals (e.g., $1.0000) using market-based pricing, and its share price will fluctuate.

UBS Select Prime Preferred Fund will, under normalcircumstances, invest more than 25% of its totalassets in the financial services group of industries.UBS Select Prime Preferred Fund may, however,invest less than 25% of its total assets in this groupof industries as a temporary defensive measure.

UBS Select Prime Preferred Fund may be subject tothe possible imposition of a liquidity fee and/ortemporary redemption gate should certain trigger-ing events occur.

UBS Select Government Preferred Fund seeks toachieve its investment objective by investing in adiversified portfolio of high quality, US governmentmoney market instruments and in related repurchaseagreements, which generally are short-term debtobligations and similar securities. They also mayinclude longer-term bonds that have variable interestrates or other special features that give them thefinancial characteristics of short-term debt. Many USgovernment money market instruments pay incomethat is generally exempt from state and local incometax, although they may be subject to corporate fran-chise tax in some states. UBS Select Government Pre-ferred Fund may invest a significant percentage of itsassets in repurchase agreements. Repurchase agree-ments are transactions in which the fund purchasesgovernment securities and simultaneously commitsto resell them to the same counterparty at a futuretime and at a price reflecting a market rate of inter-est. Income from repurchase agreements may not beexempt from state and local income taxation. Repur-chase agreements often offer a higher yield thaninvestments directly in government securities. Indeciding whether an investment in a repurchaseagreement is more attractive than a direct invest-ment in government securities, the fund considersthe possible loss of this tax advantage.

UBS Select Government Preferred Fund’s board hasdetermined that the fund will operate as a “govern-ment money market fund” pursuant to Rule 2a-7under the Investment Company Act of 1940, asamended (“Rule 2a-7”). Therefore, the fund hasadopted a policy to invest 99.5% or more of itstotal assets in cash, government securities, and/orrepurchase agreements that are collateralized fully(i.e., collateralized with cash and/or governmentsecurities). As a “government money market fund,”the fund (1) is permitted to use the amortized cost

26

UBS Series Funds

method of valuation to seek to maintain a $1.00share price, and (2) is not subject to a liquidity feeand/or a redemption gate on fund redemptionswhich might apply to other types of funds shouldcertain triggering events specified in Rule 2a-7occur. (In conformance with Rule 2a-7, UBS SelectGovernment Preferred Fund’s board has reserved itsability to change this policy with respect to liquidityfees and/or redemption gates, but such changewould only become effective after shareholderswere provided with specific advance notice of achange in the fund’s policy and have the opportu-nity to redeem their shares in accordance withRule 2a-7 before the policy change becameeffective.)

In addition, under normal circumstances, UBS SelectGovernment Preferred Fund invests at least 80% ofits net assets in US government securities, includinggovernment securities subject to repurchase agree-ments. UBS Select Government Preferred Fund’s80% policy is a “non-fundamental” policy. Thismeans that this investment policy may be changedby the fund’s board without shareholder approval.However, UBS Select Government Preferred Fundhas also adopted a policy to provide its sharehold-ers with at least 60 days’ prior written notice of anychange to the 80% investment policy.

UBS Select Treasury Preferred Fund seeks to achieveits investment objective by investing at least 80% ofits net assets (plus the amount of any borrowing forinvestment purposes) in securities issued by the USTreasury and in related repurchase agreements. Whileunder normal circumstances UBS Select Treasury Pre-ferred Fund expects to invest substantially all of itsassets in securities issued by the US Treasury and inrelated repurchase agreements, under unusual cir-cumstances, the fund may invest a portion of itsassets in other types of government securities.

UBS Select Treasury Preferred Fund’s board hasdetermined that the fund will operate as a “govern-ment money market fund” under Rule 2a-7. There-fore, in addition to the 80% policy referencedabove, the fund has adopted a policy to invest99.5% or more of its total assets in cash, govern-ment securities, and/or repurchase agreements thatare collateralized fully (i.e., collateralized with cashand/or government securities). As a “governmentmoney market fund” under Rule 2a-7, the fund(1) is permitted to use the amortized cost methodof valuation to seek to maintain a $1.00 shareprice, and (2) is not subject to a liquidity fee and/ora redemption gate on fund redemptions whichmight apply to other types of funds should certaintriggering events specified in Rule 2a-7 occur. (Inconformance with Rule 2a-7, UBS Select TreasuryPreferred Fund’s board has reserved its ability tochange this policy with respect to liquidity fees and/or redemption gates, but such change would onlybecome effective after shareholders were providedwith specific advance notice of a change in thefund’s policy and have the opportunity to redeemtheir shares in accordance with Rule 2a-7 beforethe policy change became effective.)

UBS Select Treasury Preferred Fund’s 80% policy isa “non-fundamental” policy. This means that thisinvestment policy may be changed by the fund’sboard without shareholder approval. However, UBSSelect Treasury Preferred Fund has also adopted apolicy to provide its shareholders with at least60 days’ prior written notice of any change to the80% investment policy.

UBS Select ESG Prime Preferred Fund seeks toachieve its investment objective by investing in adiversified portfolio of high quality money marketinstruments of governmental and private issuerswhile incorporating fundamental sustainability fac-tors, such as ESG performance of such issuers, intothe investment process. Money market instruments

27

UBS Series Funds

may include short-term obligations of the US gov-ernment and its instrumentalities; repurchaseagreements; obligations of issuers in the financialservices group of industries; commercial paper,other corporate obligations and asset-backed secu-rities; and municipal money market instruments.

UBS Select ESG Prime Preferred Fund calculates itsnet asset value to four decimals (e.g., $1.0000)using market based pricing, and its share price willfluctuate.

Under normal circumstances, UBS Select ESG PrimePreferred Fund invests at least 80% of its net assets(plus the amount of any borrowing for investmentpurposes), determined at the time of purchase, insecurities that meet UBS AM’s sustainability criteria.In developing its sustainability criteria, UBS AMdraws upon firm-wide resources of the UBS AssetManagement Division of UBS Group AG, of whichUBS AM is a member. UBS Select ESG Prime Pre-ferred Fund’s 80% policy is a “non-fundamental”policy. This means that this investment policy maybe changed by the fund’s board without share-holder approval. However, UBS Select ESG PrimePreferred Fund has also adopted a policy to provideits shareholders with at least 60 days’ prior writtennotice of any change to the 80% investment policy.

UBS Select ESG Prime Preferred Fund will, undernormal circumstances, invest more than 25% of itstotal assets in the financial services group of indus-tries. UBS Select ESG Prime Preferred Fund may,however, invest less than 25% of its total assets inthis group of industries as a temporary defensivemeasure.

UBS AM conducts its own credit analyses of poten-tial investments and portfolio holdings, and reliessubstantially on a dedicated proprietary creditresearch team. Embedded in the credit research pro-cess is the integration of issuer-level sustainabilityinvesting analysis as guided by the UBS Asset Man-agement Division’s approach to ESG research and

evaluation methodology. The sustainability investinganalysis provides a more comprehensive approachto security selection than credit analysis alone asinternal and external ESG ratings are applied to eval-uate the quality of sustainability practices employedby issuers. Analysts rate and maintain internal fun-damental credit and ESG ratings which form thebasis of a portfolio construction/optimizationapproach, focusing on companies that contribute tomeeting the ESG profile for the fund. Portfolio con-struction focuses on the alignment of a Rule 2a-7(the regulation governing money market funds)investment discipline with the concept of sustain-ability—the potential for long-term maintenance ofenvironmental, economic and social well-being.

Sustainability criteria includes the fundamentalanalysis of ESG risks of issuers (that is, the issuers ofthe money market instruments in which the fundmay invest), and evaluating whether, at the time ofthe fund’s investment, such issuers have better thanaverage performance in ESG practices and manag-ing ESG risks. The fundamental analysis of ESG risksmay include, but is not limited to, review of the fol-lowing factors:

• environmental responsibility• human rights and labor standards• diversity and inclusion in employment• corporate governance

UBS AM will employ a negative screening processwith regard to security selection for UBS Select ESGPrime Preferred Fund, which will exclude from thefund’s portfolio securities or sectors that manufac-ture products or engage in business activitiesviewed as having a negative social or environmentalimpact. These may include:

• controversial weapons• antipersonnel mines• cluster munitions

28

UBS Series Funds

• adult entertainment (5% revenue threshold)• tobacco producers (5% revenue threshold)• thermal coal (30% revenue threshold)• generation thermal coal (30% revenue threshold)

UBS AM may modify this list of negative screens atany time, without prior shareholder approval ornotice.

UBS Select ESG Prime Preferred Fund may be sub-ject to the possible imposition of a liquidity fee and/or temporary redemption gate should certain trig-gering events occur.

UBS AM serves as investment advisor to a range ofmoney market funds following different investmentfocuses/strategies. These include other “prime”money market funds (including UBS Select PrimePreferred Fund), which may invest in similar types ofsecurities as UBS Select ESG Prime Preferred Fund.There may be overlap between the portfolio holdingsand investments of UBS Select ESG Prime PreferredFund and other “prime” money market funds forwhich UBS AM serves as investment advisor.

Like all money market funds, each of the funds issubject to maturity, quality, diversification andliquidity requirements pursuant to Rule 2a-7. Eachof the funds’ investment strategies are designed tocomply with these requirements. Each of the fundsmay invest in high quality, short-term, US dollar-denominated money market instruments paying afixed, variable or floating interest rate.

UBS AM may use a number of professional moneymanagement techniques to respond to changingeconomic and money market conditions and toshifts in fiscal and monetary policy. These tech-niques include varying each fund’s composition andweighted average maturity based upon UBS AM’sassessment of the relative values of various money

market instruments and future interest rate pat-terns. UBS AM also may buy or sell money marketinstruments to take advantage of yield differences.

Each of the funds may maintain a rating from one ormore rating agencies that provide ratings on moneymarket funds. There can be no assurance that a fundwill maintain any particular rating or maintain it witha particular rating agency. To maintain a rating, UBSAM may manage a fund more conservatively or dif-ferently than if it were not rated.

Additional information about principal risksThe main risks of investing in the funds aredescribed below. As indicated below, not all ofthese risks apply to each fund. The fund(s) to whichthe main risks apply are noted below.

Other risks of investing in a fund, along with fur-ther details about some of the risks describedbelow, are discussed in the funds’ Statement ofAdditional Information (“SAI”). Information on howyou can obtain the SAI can be found on the backcover of this prospectus.

Credit risk (All funds). Credit risk is the risk thatthe issuer of money market instruments or financialinstitutions that have entered into repurchaseagreements with a fund will not make principal orinterest payments when they are due or completetransactions. Even if an issuer or counterparty doesnot default on a payment, a money market instru-ment’s value may decline if the market believes thatthe issuer or counterparty has become less able, orless willing, to make payments on time. Even thehighest quality money market instruments are sub-ject to some credit risk. The credit quality of anissuer or counterparty can change rapidly due tomarket developments and may affect the fund’sshare price.

29

UBS Series Funds

Interest rate risk (All funds). The value of moneymarket instruments generally can be expected tofall when short-term interest rates rise and to risewhen short-term interest rates fall. Interest rate riskis the risk that interest rates will rise, so that thevalue of a fund’s investments will fall. Also, a fund’syield will tend to lag behind changes in prevailingshort-term interest rates. This means that a fund’sincome will tend to rise more slowly than increasesin short-term interest rates. Similarly, when short-term interest rates are falling, a fund’s income gen-erally will tend to fall more slowly.

A fund may face a heightened level of interest raterisk due to certain changes in monetary policy, suchas certain types of interest rate changes by theFederal Reserve. The risks associated with changinginterest rates may have unpredictable effects on themarkets and a fund’s investments. A sudden orunpredictable increase in interest rates may causevolatility in the market and may decrease liquidity inthe money market securities markets, making itharder for a fund to sell its money market invest-ments at an advantageous time. Decreased marketliquidity also may make it more difficult to valuesome or all of a fund’s money market securitiesholdings. A low interest rate environment may poseadditional risks to a fund because low yields on afund’s portfolio holdings may have an adverseimpact on a fund’s ability to provide a positive yieldto its shareholders, pay expenses out of fund assets,or minimize the volatility of a fund’s NAV per share.

Sustainability factor risk (UBS Select ESG PrimePreferred Fund). Investing primarily in investmentsthat meet ESG criteria carries the risk that UBSSelect ESG Prime Preferred Fund may forgo other-wise attractive investment opportunities, or increaseor decrease its exposure to certain types of issuersand, therefore, may underperform compared tofunds that do not consider ESG factors in the

investment process. UBS AM’s assessment of anissuer’s ESG criteria may change over time, whichcould cause the fund to hold securities that may nolonger meet UBS AM’s current ESG criteria.

Investing on the basis of ESG criteria is qualitativeand subjective by nature and there can be no assur-ance that the process utilized by any vendors ofUBS AM or any judgment exercised by UBS AM willreflect the beliefs or values of any particular inves-tor. In addition, due to constraints imposed by reg-ulations applicable to money market funds or otherconsiderations relating to credit quality, liquidity oryield, the fund may be less able to implement asfully its ESG investment strategy than non-moneymarket funds.

Market risk (All funds). The market value of afund’s investments may fluctuate as the marketsfluctuate. Market fluctuation may affect a fund’sshare price. Market risk, sometimes dramatically orunpredictably, may affect a single issuer, industry,section of the economy or geographic region, or itmay affect the market as a whole. Volatility offinancial markets can expose a fund to greater mar-ket risk, possibly resulting in greater illiquidity andvaluation risks. Moreover, market, economic, politi-cal and social conditions in one country or geo-graphic region could adversely impact market,economic, political and social conditions in othercountries or regions, including countries andregions in which a fund invests, due to increasinglyinterconnected global economies and financial mar-kets. Additionally, market conditions and legislative,regulatory, or tax developments may affect theinvestment techniques available to the advisor inconnection with managing a fund and may result inincreased regulation of the fund or its investmentsand, in turn, may adversely affect the ability of thefund to achieve its investment objective and thefund’s performance.

30

UBS Series Funds

Liquidity risk (All funds). The funds’ investmentsmay become less liquid due to market develop-ments or adverse investor perception. When thereis no willing buyer and investments cannot be read-ily sold at the desired time or price, the funds mayhave to accept a lower price or may not be able tosell an instrument at all. The inability to sell aninstrument could adversely affect a fund’s shareprice or prevent the fund from being able to takeadvantage of other investment opportunities. Thisrisk may increase during an unusually high volumeof redemption requests by even a few large inves-tors or unusual market conditions.

Management risk (All funds). There is the riskthat the investment strategies, techniques and riskanalyses employed by the advisor may not producethe desired results. The advisor may be incorrect inits assessment of a particular security or assessmentof market, interest rate or other trends, which canresult in losses to a fund.

Concentration risk (UBS Select Prime PreferredFund and UBS Select ESG Prime PreferredFund). Each of UBS Select Prime Preferred Fundand UBS Select ESG Prime Preferred Fund will investa significant portion of its assets in securities issuedby companies in the financial services group ofindustries, including US banking, non-US banking,broker-dealers, insurance companies, finance com-panies (e.g., automobile finance) and related asset-backed securities. As a result, each fund’sperformance will be significantly impacted, bothpositively and negatively, by developments in thefinancial services sector, and each fund will be moresusceptible to such developments than other fundsthat do not concentrate their investments.

Financial services sector risk (UBS Select PrimePreferred Fund and UBS Select ESG Prime Pre-ferred Fund). Investments of UBS Select Prime

Preferred Fund and UBS Select ESG Prime PreferredFund in the financial services sector may be particu-larly affected by economic cycles, business develop-ments, interest rate changes and regulatorychanges. For example, declining economic andbusiness conditions can disproportionately impactcompanies in the financial services sector due toincreased defaults on payments by borrowers. Inter-est rate increases can also adversely affect thefinancial services sector by increasing the cost ofcapital available for financial services companies. Inaddition, financial services companies are heavilyregulated by governmental entities and, as a result,political and regulatory changes can affect theoperations and financial results of such companies,potentially imposing additional costs and possiblyrestricting the businesses in which those companiesmay engage.

US Government securities risk (All funds). Creditrisk is the risk that the issuer will not make principalor interest payments when they are due. There aredifferent types of US government securities with dif-ferent relative levels of credit risk depending on thenature of the particular government support for thatsecurity. US government securities may be sup-ported by (1) the full faith and credit of the US;(2) the ability of the issuer to borrow from the USTreasury; (3) the credit of the issuing agency, instru-mentality or government sponsored entity; (4) poolsof assets (e.g., mortgage-backed securities); or(5) the US in some other way. In some cases, thereis even the risk of default. For example, for asset-backed securities there is the risk those assets willdecrease in value below the face value of the secu-rity. Similarly, for certain agency issued securitiesthere is no guarantee the US government will sup-port the agency if it is unable to meet its obliga-tions. Further, the US government and its agenciesand instrumentalities do not guarantee the marketvalue of their securities; consequently, the value of

31

UBS Series Funds

such securities will fluctuate. This may be the caseespecially when there is any controversy or ongoinguncertainty regarding the status of negotiations inthe US Congress to increase the statutory debt ceil-ing. If the US Congress is unable to negotiate anadjustment to the statutory debt ceiling, there isalso the risk that the US government may default onpayments on certain US government securities,including those held by the funds, which could havea material negative impact on the funds.

Foreign investing risk (UBS Select Prime Pre-ferred Fund and UBS Select ESG Prime Pre-ferred Fund). UBS Select Prime Preferred Fund andUBS Select ESG Prime Preferred Fund may invest inforeign money market instruments that aredenominated in US dollars. Foreign investing mayinvolve risks relating to political, social and eco-nomic developments abroad to a greater extentthan investing in the securities of US issuers. Inaddition, there are differences between US and for-eign regulatory requirements and market practices.

Municipal securities risk (UBS Select Prime Pre-ferred Fund and UBS Select ESG Prime Pre-ferred Fund). Municipal securities are subject tointerest rate, credit, illiquidity, market and politicalrisks. The ability of a municipal issuer to make pay-ments and the value of municipal securities can beaffected by uncertainties in the municipal securitiesmarket, including litigation, the strength of thelocal or national economy, the issuer’s ability toraise revenues through tax or other means, thebankruptcy of the issuer affecting the rights ofmunicipal securities holders and budgetary con-straints of local, state and federal governmentsupon which the issuer may be relying for funding.Municipal securities and issuers of municipal securi-ties may be more susceptible to downgrade, defaultand bankruptcy during periods of economic stress.In addition, the municipal securities market can be

significantly affected by political changes, includinglegislation or proposals at either the state or thefederal level to eliminate or limit the tax-exempt sta-tus of municipal security interest. Similarly, reduc-tions in tax rates may make municipal securities lessattractive in comparison to taxable securities. Legis-latures also may be unable or unwilling to appropri-ate funds needed to pay municipal securityobligations. These events can cause the value of themunicipal securities held by the fund to fall. In addi-tion, third-party credit quality or liquidity enhance-ments are frequently a characteristic of the structureof municipal securities purchased by money marketfunds. Problems encountered by such third-parties(such as issues negatively impacting a municipalsecurity insurer or bank issuing a liquidity enhance-ment facility) may negatively impact a municipalsecurity even though the related municipal issuer isnot experiencing problems. Municipal bondssecured by revenues from public housing authoritiesmay be subject to additional uncertainties relatingto the possibility that proceeds may exceed supplyof available mortgages to be purchased by publichousing authorities, resulting in early retirement ofbonds, or that homeowner repayments will createan irregular cash flow.

New fund risk (UBS Select ESG Prime PreferredFund). The fund is new with no operating history.As a result, prospective investors have no trackrecord or history on which to base their investmentdecisions. In addition, there can be no assurancethat the fund will grow to or maintain an economi-cally viable size.

Additional (non-principal) risksLIBOR replacement risk (All funds). Certain vari-able- and floating-rate debt securities that a fundmay invest in are subject to rates that are tied to aninterest rate, such as the London Interbank OfferedRate (“LIBOR”). In 2017, the United Kingdom’s

32

UBS Series Funds

Financial Conduct Authority (“FCA”) warned thatLIBOR may cease to be available or appropriate foruse by 2021. There remains uncertainty regardingthe future utilization of LIBOR and the nature ofany replacement rate. The unavailability or replace-ment of LIBOR may affect the value, liquidity orreturn on certain fund investments and may resultin costs incurred in connection with closing outpositions and entering into new trades. Any pricingadjustments to a fund’s investments resulting froma substitute reference rate may also adversely affectthe fund’s performance and/or net asset value.

Securities lending risk (All funds). Securitieslending involves the lending of portfolio securitiesowned by a fund to qualified broker-dealers andfinancial institutions. When lending portfolio securi-ties, a fund initially will require the borrower to pro-vide the fund with collateral, most commonly cash,which the fund will invest. Although a fund investsthis collateral in a conservative manner, it is possiblethat it could lose money from such an investmentor fail to earn sufficient income from its investmentto cover the fee or rebate that it has agreed to paythe borrower. Loans of securities also involve a riskthat the borrower may fail to return the securitiesor deliver the proper amount of collateral, whichmay result in a loss to a fund. In addition, in theevent of bankruptcy of the borrower, a fund couldexperience losses or delays in recovering the loanedsecurities. In some cases, these risks may be miti-gated by an indemnification provided by the funds’lending agent.

Temporary and defensive positioning (Allfunds). During adverse market conditions or whenthe advisor believes there is an insufficient supply ofappropriate money market securities in which toinvest, a fund may temporarily hold uninvested cashin lieu of such investments. During periods whensuch temporary or defensive positions are held, a

fund may not be able to fully pursue its investmentobjective. Such positions may also subject a fund toadditional costs and risks, such as increased expo-sure to cash held at a custodian bank.

Structured security risk (UBS Select Prime Pre-ferred Fund and UBS Select ESG Prime Pre-ferred Fund). UBS Select Prime Preferred Fund andUBS Select ESG Prime Preferred Fund may purchasesecurities representing interests in underlying assets,but structured to provide certain advantages notinherent in those assets (e.g., enhanced liquidity andyields linked to short-term interest rates). If thosesecurities behaved in a way that the advisor did notanticipate, or if the security structures encounteredunexpected difficulties, a fund could suffer a loss.Structured securities represent a significant portionof the short-term securities markets.

33

UBS Series Funds

Managing your fund account

The following pages tell you how to buy, sell andexchange shares of each fund.

If you are buying fund shares directly or throughfinancial intermediaries, you should refer to the fol-lowing section regarding buying, selling orexchanging fund shares in most cases. If you arebuying shares through UBS Financial ServicesInc.’s automated purchasing account system,you should direct your request to your finan-cial advisor and refer to the sections belowbeginning “UBS Financial Services Inc.: auto-mated purchasing accounts” on page 40 of thisprospectus.

Buying sharesThe funds accept the settlement of purchase ordersonly in available federal funds deposited by a com-mercial bank in an account at a Federal ReserveBank, which can be transferred to a similar accountof another bank in one day and may be made imme-diately available to a fund through its custodian.

You may buy fund shares through financialintermediaries who are authorized to accept pur-chase orders on behalf of the funds. If you buy fundshares through a financial intermediary who holdsthem in its own name on your behalf (in “streetname”), the financial intermediary is responsible forsending the order to the transfer agent. You maynot call the funds’ transfer agent directly if yourshares are held in “street name,” but should directall your requests to buy, sell or exchange sharesdirectly to your financial intermediary.

If you do not use a financial intermediary, you mayalso buy fund shares directly by calling the funds’transfer agent, BNY Mellon Investment Servicing(US) Inc. (“BNY Mellon”), at 1-888-547 FUND and

speaking to a representative. If you buy fund sharesdirectly, you will need to complete an accountapplication in connection with your initial purchase.You can get a copy of the application from UBSAsset Management (US) Inc., the fund’s distributor(“UBS AM (US)”), or a financial intermediary or bycalling the transfer agent toll-free 1-888-547 FUND.

You buy shares at the net asset value next deter-mined after receipt of your purchase order in goodform by the transfer agent. A fund must receivepayment on the same day. Your purchase order willbe effective only if (1) you or your financial interme-diary wires payment in federal funds on the samebusiness day that you place your order, and (2) thewire is actually credited to the fund’s bank accountby a Federal Reserve Bank on that day. Otherwise,the order will be rejected. A business day is any dayon which the Federal Reserve Bank of New York,the New York Stock Exchange (“NYSE”), and theprincipal bond markets (as recommended by theSecurities Industry and Financial Markets Associa-tion (“SIFMA”)) are open. (Holidays are listed onAppendix A to this prospectus.)

The charts below show processing times by whichorders received by the funds’ transfer agent willnormally be executed. All times shown below repre-sent Eastern time. Financial intermediaries mayimpose additional guidelines for when orders mustbe placed.

34

UBS Series Funds

For UBS Select Government Preferred Fundand UBS Select Treasury Preferred Fund:

If a purchase order is received:The order will normally

be executed as of:

By 9:00 a.m. 9:00 a.m.

After 9:00 a.m. andbefore 10:00 a.m.

10:00 a.m.


11:00 a.m.

After 11:00 a.m. andbefore 12:00 (noon)

12:00 (noon)

After 12:00 (noon) andbefore 1:00 p.m.

1:00 p.m.

After 1:00 p.m. andbefore 2:00 p.m.

2:00 p.m.


3:00 p.m.


4:00 p.m.


5:00 p.m.

For UBS Select Prime Preferred Fund and UBSSelect ESG Prime Preferred Fund:


be executed as of:

By 8:00 a.m. 8:00 a.m.


12:00 (noon)


3:00 p.m.

Each fund may advance the time by which orders tobuy or sell its shares must be received by the trans-fer agent on any day that the NYSE closes earlybecause trading has been halted for the day. UBSSelect Government Preferred Fund and UBS Select

Treasury Preferred Fund will advance the final timeby which orders to buy or sell shares must bereceived by the transfer agent to 3:00 p.m.(Eastern time) on those days that SIFMA has recom-mended that the bond markets close early. (Thenormal deadline by which orders to buy or sellshares of UBS Select Prime Preferred Fund and UBSSelect ESG Prime Preferred Fund must be receivedby the transfer agent is 3:00 p.m. (Eastern time).)Appendix A to this prospectus lists the SIFMA US“early closing” holiday recommendations schedulefor the remainder of 2019 and for 2020. These“early closing” days most often occur on a businessday prior to a national holiday.

The funds, UBS AM and UBS AM (US) have theright to reject a purchase order and to suspend theoffering of fund shares for a period of time or per-manently. UBS AM (US) may return without noticemoney wired to a fund if the investor fails to placea corresponding share purchase order.

Wire instructions. You may instruct your bank totransfer federal funds by wire to:

Bank Name: Bank of New York MellonABA: 011001234Credit: 000073-5515

BNY Mellon Investment Servicing(US) Inc. as Agent for UBS Funds

Further Credit: Beneficiary Fund/Account Number(Shareholder account number)

You should not wire money directly to the funds’transfer agent if your shares are held in “streetname,” as described above in “Buying shares.” Afinancial intermediary or your bank may impose aservice charge for wire transfers.

Minimum investment. The minimum investmentlevel for initial purchases of UBS Select Prime Pre-ferred Fund and UBS Select ESG Prime Preferred

35

UBS Series Funds

Fund generally is $99,000,000. The minimum invest-ment level for initial purchases of UBS Select Govern-ment Preferred Fund and UBS Select TreasuryPreferred Fund generally is $50,000,000.

Subsequent purchases, and purchases throughexchanges, are not subject to a minimum invest-ment level.

UBS AM (US) may waive these minimums underother circumstances in its discretion. The funds maychange their minimum investment requirements atany time. Investments must be denominated inUS dollars.

If your fund account balance has fallen below therespective minimum initial investment amount indi-cated above, UBS AM (US) reserves the right toreject your purchase order to add to the accountunless the account balance will be at least suchamount after that purchase.

Electronic trade entry. The funds may offer anelectronic trade order entry capability to eligibleinstitutional investors who meet certain condi-tions. This option is not available if your sharesare held in “street name,” as described above in“Buying shares.” For more information about thisoption and its availability, contact your invest-ment professional at your financial intermediary,or contact the transfer agent at 1-888-547 FUND.

Selling sharesYou may sell your shares through financialintermediaries that are authorized to acceptredemption requests. If you sell your sharesthrough a financial intermediary who holds them inits own name on your behalf (in “street name”),the financial intermediary is then responsible forsending the order to the transfer agent. You maynot call the funds’ transfer agent directly if your

shares are held in “street name,” but should directall your requests to buy, sell or exchange sharesdirectly to your financial intermediary.

You may also sell your shares by calling the transferagent directly at 1-888-547 FUND and speakingwith a representative.

You sell shares based upon the net asset value nextdetermined after receipt of your redemption orderin good form by the transfer agent. A redemptionorder will not be in good form unless it is receivedby the fund’s transfer agent prior to the deadlinesset forth below. Orders that are not received ingood form will not be executed at the net assetvalue next determined after receipt of the order.Orders to sell shares of UBS Select Government Pre-ferred Fund and UBS Select Treasury Preferred Fundreceived by the funds’ transfer agent before9:00 a.m. (Eastern time) will normally be executedas of 9:00 a.m. (Eastern time). Orders to sell sharesof UBS Select Prime Preferred Fund and UBS SelectESG Prime Preferred Fund received by the funds’transfer agent by 8:00 a.m. (Eastern time) will nor-mally be executed as of 8:00 a.m. (Eastern time).

The charts below show processing times by whichorders received by the funds’ transfer agent willnormally be executed. All times shown below repre-sent Eastern time.

36

UBS Series Funds


If a redemption order is received:The order will normally

be executed as of:

By 9:00 a.m. 9:00 a.m.


10:00 a.m.


11:00 a.m.


12:00 (noon)


1:00 p.m.


2:00 p.m.


3:00 p.m.


4:00 p.m.


5:00 p.m.



be executed as of:

By 8:00 a.m. 8:00 a.m.


12:00 (noon)


3:00 p.m.

As noted above under “Buying shares,” each fundmay advance the time for the transfer agent’s receiptof orders to sell shares (e.g., days on which securitiesmarkets close early prior to a national holiday).

Your sales proceeds will be paid in federal funds.Proceeds from the sale will be wired to one or moreaccounts you have designated. If a redemptionorder is received by 5:00 p.m. (Eastern time) forUBS Select Government Preferred Fund and UBSSelect Treasury Preferred Fund, or by 3:00 p.m.(Eastern time) for UBS Select Prime Preferred Fundand UBS Select ESG Prime Preferred Fund, the pro-ceeds ordinarily will be transmitted in federal fundson the same day. If you sell all the shares you own,dividends accrued for the month to date will bepaid in federal funds and wired on the same day tothe accounts noted above.

If the transfer agent receives your order to sellshares late in the day, it will process your order andinitiate a wire. However, your bank account or youraccount at your financial intermediary may notreceive the proceeds in a timely manner if a FederalReserve Bank is experiencing delay in transfer offunds. Neither the funds, UBS AM, UBS AM (US), afinancial intermediary nor the transfer agent isresponsible for the performance of a bank or any ofits intermediaries.

The transfer agent will process orders to sell sharesonly if you have on file with it a properly completedaccount application with a signature guarantee (ifyou have previously completed one in connectionwith a direct purchase of fund shares), or otherauthentication acceptable to the transfer agent. Theaccount application requires you to designate theaccount(s) for wiring sales proceeds. You must sub-mit any change in the designated account(s) for saleproceeds in a form acceptable to the transfer agent.The transfer agent will not place the sales order if theinformation you provide does not correspond to theinformation on your application or account records.

A signature guarantee may be obtained from afinancial institution, broker, dealer or clearing

37

UBS Series Funds

agency that is a participant in one of the medallionprograms recognized by the Securities TransferAgents Association. These are: Securities TransferAgents Medallion Program (STAMP), StockExchanges Medallion Program (SEMP) and the NewYork Stock Exchange Medallion Signature Program(MSP). The transfer agent will not accept signatureguarantees that are not part of these programs.

Typically, redemptions of fund shares will be madeby the funds wiring cash payments. The funds typi-cally expect to meet redemption requests by usingholdings of cash or cash equivalents and/or pro-ceeds from the sale or maturity of portfolio hold-ings. Although not routinely used by a fund, a fundreserves the right to pay proceeds “in kind” (i.e.,payment in securities rather than cash) if the invest-ment you are redeeming is large enough to affect afund’s operations or in particularly stressed marketconditions. In these cases, you might incur transac-tion costs converting the securities to cash. Thesecurities included in a redemption in kind mayinclude illiquid securities that may not be immedi-ately saleable.

If you have additional questions on selling shares,you should contact your investment professional atyour financial intermediary or call the transfer agentat 1-888-547 FUND.

Exchanging sharesYou may exchange shares of a fund (except UBSSelect Prime Preferred Fund and UBS Select ESGPrime Preferred Fund) for shares of another fundoffered in this prospectus (except UBS Select PrimePreferred Fund and UBS Select ESG Prime PreferredFund) or of UBS Prime Preferred Fund and of UBSTax-Free Preferred Fund. UBS Prime Preferred Fundand UBS Tax-Free Preferred Fund have different eligi-bility requirements for purchase, and you may not beable to exchange your shares if you are not eligible

to purchase shares of those other funds, which limitinvestors to “natural persons” as described in theirprospectus.

Exchanges between UBS Select Prime PreferredFund, UBS Select ESG Prime Preferred Fund andother funds are not permitted.

The minimums noted above in “Buying shares” donot apply to initial purchases made through anexchange of shares. All exchanges are based uponthe net asset value that is next calculated after thefund receives your order.

Exchange orders for each of UBS Select GovernmentPreferred Fund and UBS Select Treasury PreferredFund are normally accepted up until 5:00 p.m.(Eastern time). Exchange orders received after thattime will not be effected, and you or your financialintermediary will have to place an exchange orderbefore that time on the following business day if youstill wish to effect an exchange. If you exchange allyour fund shares, the dividends accrued on thoseshares for the month to date will also be invested inthe shares of the other fund into which theexchange is made.

You can place an exchange order through a finan-cial intermediary. The financial intermediary is thenresponsible for sending the order to the transferagent. You may not call the funds’ transfer agentdirectly if your shares are held in “street name,”but should direct all your requests to buy, sell orexchange shares directly to your financialintermediary.

You can also place an exchange order by calling thetransfer agent directly at 1-888-547 FUND andspeaking with a representative.

Shareholders making their initial purchase ofanother fund through an exchange should allow

38

UBS Series Funds

more time. These exchange orders should bereceived by the transfer agent at least one half hourbefore the exchange order deadline to allow thetransfer agent sufficient time to establish anaccount in the new fund. The transfer agent maynot be able to effect the exchange if this extra timeis not allotted.

The funds may modify or terminate the exchangeprivilege at any time.

Transfer of account limitationsIf you hold your shares with UBS Financial ServicesInc. or another securities firm, please note that ifyou change securities firms, you may not be able totransfer your fund shares to an account at the newsecurities firm. Fund shares may only be transferredto an account held with a securities dealer or finan-cial intermediary that has entered into an agree-ment with the fund’s principal underwriter. If youcannot transfer your shares to another firm, youmay choose to hold the shares directly in your ownname with the fund’s transfer agent, BNY Mellon.Please contact your broker or Financial Advisor forinformation on how to transfer your shares to thefund’s transfer agent. If you transfer your shares tothe fund’s transfer agent, the fund’s principalunderwriter may be named as the dealer of record,and you will receive ongoing account statementsfrom BNY Mellon. Should you have any questionsregarding the portability of your fund shares, pleasecontact your broker or Financial Advisor.

Additional information about your accountYou will receive a confirmation of your initial pur-chase of fund shares, and subsequent transactionsmay be reported on periodic account statements.These periodic statements may be sent monthlyexcept that, if your only fund activity in a quarterwas reinvestment of dividends, the activity may bereported on a quarterly rather than a monthlystatement.

To help the government fight the funding of terror-ism and money laundering activities, federal lawrequires all financial institutions to obtain, verifyand record information that identifies each personwho opens an account. If you do not provide theinformation requested, a fund may not be able tomaintain your account. If a fund is unable to verifyyour identity (or that of another person(s) autho-rized to act on your behalf) within a reasonabletime, the fund and UBS AM (US) reserve the rightto close your account and/or take such other actionthey deem reasonable or required by law. If wedecide to close your account for this reason, yourfund shares will be redeemed at the net asset valueper share next calculated after the account isclosed, less any applicable fees. You may recognizea gain or loss on the redemption of your fundshares and you may incur a tax liability.

Upon receipt of a proper redemption request sub-mitted in a timely manner and otherwise in accor-dance with the redemption procedures set forth inthis prospectus, each fund will redeem therequested shares and make a payment to you insatisfaction thereof no later than the business dayfollowing the redemption request (under normalcircumstances, on the same day). Each fund maypostpone and/or suspend redemption and pay-ment beyond one business day (but within sevencalendar days) for any period during which there isa non-routine closure of Fedwire or applicableFederal Reserve Banks. In addition, each fund mayalso postpone or suspend redemption and pay-ment as follows: (1) for any period (a) duringwhich the New York Stock Exchange (“NYSE”) isclosed other than customary weekend and holidayclosings or (b) during which trading on the NYSE isrestricted; (2) for any period during which anemergency exists as a result of which (a) disposalby the fund of securities owned by it is not reason-ably practicable or (b) it is not reasonably practica-ble for the fund fairly to determine the net asset

39

UBS Series Funds

value of shares of the fund; (3) for any period dur-ing which the US Securities and Exchange Com-mission (“SEC”) has, by rule or regulation,deemed that (a) trading shall be restricted or(b) an emergency exists; (4) for any period that theSEC may by order permit for your protection;(5) for any period during which the fund, as partof a necessary liquidation of the fund, has properlypostponed and/ or suspended redemption ofshares and payment in accordance with federalsecurities laws; or (6) with respect to UBS SelectPrime Preferred Fund and UBS Select ESG PrimePreferred Fund, if the board determines to imposea redemption gate in accordance with Rule 2a-7(see “Information on liquidity fees and redemptiongates (UBS Select Prime Preferred Fund and UBSSelect ESG Prime Preferred Fund)” below).

A financial intermediary buying or selling shares forits customers is responsible for transmitting ordersto the transfer agent in accordance with its cus-tomer agreements and the procedures notedabove.

UBS AM (US) (not the funds) also may pay fees toentities that make shares of the funds available toothers. The amount of these fees will be negotiatedbetween UBS AM (US) and the entity.

If you currently have an account at UBS FinancialServices Inc. and prefer the features of an Auto-mated Purchasing Account (as described below),ask your Financial Advisor to help you to open anAutomated Purchasing Account. You will need toredeem your shares in your Direct PurchasingAccount (as described below) and to transfer theproceeds to a new Automated Purchasing Account.More information regarding Automated PurchasingAccounts is provided below.

UBS Financial Services Inc.: automatedpurchasing accountsInitial purchases made through UBS Financial Ser-vices Inc. can be made in one of two ways. Thepurchases can be made by your Financial Advisordirectly with a fund (a “Direct PurchasingAccount”) or can be entered through that firm’sorder entry system (an “Automated PurchasingAccount”). Your account will be established as anAutomated Purchasing Account unless you instructyour Financial Advisor otherwise. Automated Pur-chasing Accounts will have certain benefits but donot have certain features available to Direct Pur-chasing Accounts.

If you have an Automated Purchasing Account, youshould direct all your requests to buy, sell orexchange shares directly to your Financial Advisor.The following sections provide information regardingAutomated Purchasing Accounts; procedures relatedto Direct Purchasing Accounts are described aboveunder “Managing your fund account.”

Buying sharesWhen you instruct your Financial Advisor to buyshares on your behalf, your account at UBS Finan-cial Services Inc. will automatically be debited, andUBS Financial Services Inc. will wire funds on yourbehalf. Your Financial Advisor is responsible formaking sure that your order is promptly sent to afund.

Shares are available to Automated PurchasingAccounts as an economical and convenient meansto invest short-term funds.

You buy shares at the net asset value next deter-mined after receipt of your purchase order in goodform by the transfer agent. The fund must receivepayment on the same day. Your purchase order willbe effective only if (1) UBS Financial Services Inc.

40

UBS Series Funds

wires payment in federal funds on the same busi-ness day that you place your order, and (2) the wireis actually credited to the fund’s bank account by aFederal Reserve Bank on that day. Otherwise, theorder will be rejected. A business day is any day onwhich the Federal Reserve Bank of New York, theNYSE, and the principal bond markets (as recom-mended by SIFMA) are open. (Holidays are listed onAppendix A to this prospectus.)




be executed as of:

By 9:00 a.m. 9:00 a.m.


10:00 a.m.


11:00 a.m.


12:00 (noon)


1:00 p.m.


2:00 p.m.


3:00 p.m.


4:00 p.m.


5:00 p.m.



be executed as of:

By 8:00 a.m. 8:00 a.m.


12:00 (noon)


3:00 p.m.

Each fund may advance the time by which orders tobuy or sell its shares must be received by the trans-fer agent on any day that the NYSE closes earlybecause trading has been halted for the day. UBSSelect Government Preferred Fund and UBS SelectTreasury Preferred Fund will advance the final timeby which orders to buy or sell shares must bereceived by the transfer agent to 3:00 p.m.(Eastern time) on those days that SIFMA has recom-mended that the bond markets close early. (Thenormal deadline by which orders to buy or sellshares of UBS Select Prime Preferred Fund and UBSSelect ESG Prime Preferred Fund must be receivedby the transfer agent is 3:00 p.m. (Eastern time).)Appendix A to this prospectus lists the SIFMA USholiday “early closing” recommendations schedulefor the remainder of 2019 and for 2020. These“early closing” days most often occur on a businessday prior to a national holiday.

The funds, UBS AM and UBS AM (US) have theright to reject a purchase order and to suspend theoffering of fund shares for a period of time orpermanently.

Minimum investment. The minimum investmentlevel for initial purchases of UBS Select Prime Pre-ferred Fund and UBS Select ESG Prime PreferredFund generally is $99,000,000. The minimuminvestment level for initial purchases of UBS Select

41

UBS Series Funds

Government Preferred Fund and UBS Select Trea-sury Preferred Fund generally is $50,000,000. Sub-sequent purchases, and purchases throughexchanges, are not subject to a minimum invest-ment level. UBS AM (US) may waive this minimumunder other circumstances in its discretion. Thefunds may change their minimum investmentrequirements at any time. Investments must bedenominated in US dollars.

If your fund account balance has fallen below therespective minimum initial investment amount indi-cated above, UBS AM (US) reserves the right toreject your purchase order to add to the accountunless the account balance will be at least suchamount after that purchase.

Selling sharesYou must place your sell order directly with yourFinancial Advisor. Your Financial Advisor is responsi-ble for making sure that your order is promptly sentto a fund.

You sell shares based upon the net asset value nextdetermined after receipt of your redemption orderin good form by the transfer agent. A redemptionorder will not be in good form unless it is receivedby the fund’s transfer agent prior to the deadlinesset forth below. Orders that are not received ingood form will not be executed at the net assetvalue next determined after receipt of the order.Orders to sell shares of UBS Select Government Pre-ferred Fund and UBS Select Treasury Preferred Fundreceived by the funds’ transfer agent before9:00 a.m. (Eastern time) will normally be executedas of 9:00 a.m. (Eastern time). Orders to sell sharesof UBS Select Prime Preferred Fund and UBS SelectESG Prime Preferred Fund received by the funds’transfer agent by 8:00 a.m. (Eastern time) will nor-mally be executed as of 8:00 a.m. (Eastern time).




be executed as of:

By 9:00 a.m. 9:00 a.m.


10:00 a.m.


11:00 a.m.


12:00 (noon)


1:00 p.m.


2:00 p.m.


3:00 p.m.


4:00 p.m.


5:00 p.m.



be executed as of:

By 8:00 a.m. 8:00 a.m.


12:00 (noon)


3:00 p.m.

42

UBS Series Funds

As noted above under “Buying shares,” a fund mayadvance the time for the transfer agent’s receipt oforders to sell shares (e.g., days on which securitiesmarkets close early prior to a national holiday).

Your sales proceeds will be paid in federal funds wireddirectly to UBS Financial Services Inc. for credit to youraccount ordinarily on the same day. If you sell all theshares you own, dividends accrued for the monthto date will be paid in federal funds and wired ordeposited on the same day.

If the transfer agent receives your order to sell shareslate in the day, it will process your order and initiatea wire. However, your account at UBS Financial Ser-vices Inc. may not receive the proceeds in a timelymanner if a Federal Reserve Bank is experiencingdelay in transfer of funds. Neither the funds, UBSAM, UBS AM (US), UBS Financial Services Inc. nor thetransfer agent is responsible for the performance ofa bank or any of its intermediaries.

Typically, redemptions of fund shares will be madeby the funds wiring cash payments or deposit intoyour account. The funds typically expect to meetredemption requests by using holdings of cash orcash equivalents and/or proceeds from the sale ormaturity of portfolio holdings. Although not rou-tinely used by a fund, a fund reserves the right topay proceeds “in kind” (i.e., payment in securitiesrather than cash) if the investment you are redeem-ing is large enough to affect a fund’s operations orin particularly stressed market conditions. In thesecases, you might incur brokerage costs convertingthe securities to cash. The securities included in aredemption in kind may include illiquid securitiesthat may not be immediately saleable.

If you have additional questions on selling shares,you should contact your Financial Advisor or call thetransfer agent at 1-888-547 FUND.

Exchanging sharesYou must place your exchange order directly withyour Financial Advisor, who is responsible for send-ing the order to the transfer agent.

You may exchange shares of a fund (except UBSSelect Prime Preferred Fund and UBS Select ESGPrime Preferred Fund) for shares of another fundoffered in this prospectus (except UBS Select PrimePreferred Fund and UBS Select ESG Prime PreferredFund) or of UBS Prime Preferred Fund and of UBSTax-Free Preferred Fund. UBS Prime Preferred Fundand UBS Tax-Free Preferred Fund have different eli-gibility requirements for purchase, and you may notbe able to exchange your shares if you are not eligi-ble to purchase shares of those other funds, whichlimit investors to “natural persons” as described intheir prospectus.

Exchanges between UBS Select Prime PreferredFund, UBS Select ESG Prime Preferred Fund andother funds are not permitted.

The minimums noted above in “Buying shares” donot apply to initial purchases made through anexchange of shares. All exchanges are based uponthe net asset value that is next calculated after thefund receives your order.

Exchange orders for each of UBS Select Govern-ment Preferred Fund and UBS Select Treasury Pre-ferred Fund are normally accepted up until5:00 p.m. (Eastern time). Exchange orders receivedafter that time will not be effected, and you willneed to instruct your Financial Advisor to place anexchange order before that time on the followingbusiness day if you still wish to effect an exchange.If you exchange all your fund shares, the dividendsaccrued on those shares for the month to date willalso be invested in the shares of the other fund intowhich the exchange is made.

43

UBS Series Funds

Shareholders making their initial purchase of anotherfund through an exchange should allow more time.These exchange orders should be received by thetransfer agent at least one half hour before theexchange order deadline to allow the transfer agentsufficient time to establish an account in the newfund. Otherwise the transfer agent may not be able toeffect the exchange if this extra time is not allotted.

The funds may modify or terminate the exchangeprivilege at any time.

Transfer of account limitationsIf you hold your shares with UBS Financial ServicesInc. or another securities firm, please note that ifyou change securities firms, you may not be able totransfer your fund shares to an account at the newsecurities firm. Fund shares may only be transferredto an account held with a securities dealer or finan-cial intermediary that has entered into an agree-ment with the fund’s principal underwriter. If youcannot transfer your shares to another firm, youmay choose to hold the shares directly in your ownname with the fund’s transfer agent, BNY Mellon.Please contact your broker or Financial Advisor forinformation on how to transfer your shares to thefund’s transfer agent. If you transfer your shares tothe fund’s transfer agent, the fund’s principalunderwriter may be named as the dealer of record,and you will receive ongoing account statementsfrom BNY Mellon. Should you have any questionsregarding the portability of your fund shares, pleasecontact your broker or Financial Advisor.

Additional information about your accountYou will receive a confirmation of your initial purchaseof fund shares, and subsequent transactions may bereported on periodic account statements. These peri-odic statements may be sent monthly except that, ifyour only fund activity in a quarter was reinvestmentof dividends, the activity may be reported on a quar-terly rather than a monthly statement.

To help the government fight the funding of terror-ism and money laundering activities, federal lawrequires all financial institutions to obtain, verifyand record information that identifies each personwho opens an account. If you do not provide theinformation requested, a fund may not be able tomaintain your account. If a fund is unable to verifyyour identity or that of another person(s) autho-rized to act on your behalf, the fund and UBS AM(US) reserve the right to close your account and/ortake such other action they deem reasonable orrequired by law. Fund shares will be redeemed andvalued in accordance with the net asset value nextcalculated after the determination has been madeto close the account.

Upon receipt of a proper redemption request sub-mitted in a timely manner and otherwise in accor-dance with the redemption procedures set forth inthis prospectus, each fund will redeem the requestedshares and make a payment to you in satisfactionthereof no later than the business day following theredemption request (under normal circumstances, onthe same day). Each fund may postpone and/or sus-pend redemption and payment beyond one businessday (but within seven calendar days) for any periodduring which there is a non-routine closure ofFedwire or applicable Federal Reserve Banks. In addi-tion, each fund may also postpone or suspendredemption and payment as follows: (1) for anyperiod (a) during which the NYSE is closed otherthan customary weekend and holiday closings or(b) during which trading on the NYSE is restricted;(2) for any period during which an emergency existsas a result of which (a) disposal by the fund of secu-rities owned by it is not reasonably practicable or(b) it is not reasonably practicable for the fund fairlyto determine the net asset value of shares of thefund; (3) for any period during which the SEC has,by rule or regulation, deemed that (a) trading shallbe restricted or (b) an emergency exists; (4) for anyperiod that the SEC may by order permit for your

44

UBS Series Funds

protection; (5) for any period during which the fund,as part of a necessary liquidation of the fund, hasproperly postponed and/or suspended redemption ofshares and payment in accordance with federal secu-rities laws; or (6) with respect to UBS Select PrimePreferred Fund and UBS Select ESG Prime PreferredFund, if the board determines to impose a redemp-tion gate in accordance with Rule 2a-7 (see “Infor-mation on liquidity fees and redemption gates (UBSSelect Prime Preferred Fund and UBS Select ESGPrime Preferred Fund)” below).

UBS AM (US) (not the funds) also may pay fees toentities that make shares of the funds available toothers. The amount of these fees will be negotiatedbetween UBS AM (US) and the entity.

If you currently have an Automated PurchasingAccount and prefer the features of a Direct Purchas-ing Account as described above, ask your FinancialAdvisor to help you to open a Direct PurchasingAccount. You need to complete an account applica-tion when establishing a Direct Purchasing Account.

Information on liquidity fees and redemptiongates (UBS Select Prime Preferred Fund andUBS Select ESG Prime Preferred Fund)Pursuant to Rule 2a-7, each of Prime Master Fund’sand ESG Prime Master Fund’s board is permitted toimpose a liquidity fee on redemptions from the rel-evant master fund (up to 2%) or a redemption gateto temporarily restrict redemptions from the rele-vant master fund for up to 10 business days (in any90-day period) in the event that the relevant masterfund’s “weekly liquid assets” fall below certain des-ignated thresholds. The impact of any such liquidityfee or redemption gate will flow through to each ofthe relevant feeder funds, which will implement acorresponding liquidity fee or redemption gate.Weekly liquid assets generally include cash, directobligations of the US government, certain other US

government or agency securities, securities that willmature or are subject to a demand feature that isexercisable and payable within five business days,and amounts receivable and due unconditionallywithin five business days on pending sales of port-folio securities.

If either of Prime Master Fund’s or ESG Prime MasterFund’s weekly liquid assets fall below 30% of therelevant master fund’s total assets, the relevantmaster fund’s board is permitted, but not required,to: (i) impose a liquidity fee of no more than 2% ofthe amount redeemed; and/or (ii) impose a redemp-tion gate to temporarily suspend the right ofredemption. If either of Prime Master Fund’s or ESGPrime Master Fund’s weekly liquid assets fall below10% of the relevant master fund’s total assets, therelevant master fund and thus, the relevant feederfund, must impose, generally as of the beginning ofthe next business day, a liquidity fee of 1% of theamount redeemed unless the relevant master fund’sboard determines that such a fee would not be inthe best interests of such master fund or determinesthat a lower or higher fee (subject to the 2% limit)would be in the best interests of such master fund.

Liquidity fees and redemption gates are most likelyto be imposed only during times of extraordinarymarket stress or exceptional circumstances pertain-ing to a fund. The imposition and termination of aliquidity fee or redemption gate will be reported bya fund to the SEC on Form N-CR. Such informationwill also be available on a fund’s websitehttps://www.ubs.com/usmoneymarketfunds. Inaddition, a fund may make such announcementsthrough a press release or by other means.

Liquidity fees would reduce the amount you receiveupon redemption of your shares. A fund retains theliquidity fees for the benefit of remaining share-holders. Any redemption requests submitted while

45

UBS Series Funds

a redemption gate is in place will be cancelled with-out further notice. A new redemption request mustbe submitted to a fund if you wish to redeem yourshares after the redemption gate has been lifted.

Each of Prime Master Fund’s and ESG Prime MasterFund’s board may, in its discretion, terminate aliquidity fee or redemption gate at any time if itbelieves such action to be in the best interest of therelevant master fund and its interestholders. Also,liquidity fees and redemption gates will automati-cally terminate at the beginning of the next busi-ness day once weekly liquid assets reach at least30% of the relevant master fund’s total assets.Redemption gates may only last up to 10 businessdays in any 90-day period. When a fee or a gate isin place, a fund may cease selling shares or subjectthe purchase of shares to certain conditions, whichmay include affirmation of the investor’s knowl-edge that a fee or a gate is in effect. Each of PrimeMaster Fund’s and ESG Prime Master Fund’s boardmay, in its discretion, permanently suspendredemptions and liquidate the relevant master fundand, thus, the corresponding feeder fund, if,among other things, the relevant master fund, atthe end of a business day, has less than 10% of itstotal assets invested in weekly liquid assets.

There is some degree of uncertainty with respect tothe tax treatment of liquidity fees received bymoney market funds, and such tax treatment maybe the subject of future guidance issued by the IRS.If the fund receives liquidity fees, it will consider theappropriate tax treatment of such fees to the fundat such time.

(The board of Government Master Fund and Trea-sury Master Fund has determined not to subjectGovernment Master Fund and Treasury MasterFund and thus, UBS Select Government PreferredFund and UBS Select Treasury Preferred Fund, to a

liquidity fee and/or a gate on redemptions. Pleasenote that the board of Government Master Fundand Treasury Master Fund has reserved its ability tochange this policy in the future, but only after pro-viding prior notice to shareholders.)

Market timingFrequent purchases and redemptions of fund sharescould increase each fund’s transaction costs, such asmarket spreads and custodial fees, and may inter-fere with the efficient management of each fund’sportfolio, which could impact each fund’s perfor-mance. However, money market funds are generallyused by investors for short-term investments, oftenin place of bank checking or savings accounts or forcash management purposes. Investors value theability to add and withdraw their funds quickly,without restriction. UBS AM (US) anticipates thatshareholders will purchase and sell fund shares fre-quently because each fund is designed to offerinvestors a liquid cash option. UBS AM (US) alsobelieves that money market funds, such as thefunds offered in this prospectus, are not targets ofabusive trading practices. For these reasons, theboard has not adopted policies and procedures, orimposed redemption fees or other restrictions suchas minimum holding periods, to discourage exces-sive or short-term trading of fund shares.

Other UBS funds that are managed by UBS AM thatare not money market funds have approved policiesand procedures designed to discourage and preventabusive trading practices. For more informationabout market timing policies and procedures forthese funds, please see the funds’ prospectuses.

Pricing and valuationThe price of fund shares is based on net asset value.The net asset value per share is equal to the value ofall the assets of the fund, minus the liabilities of thefund, divided by the number of shares outstanding.

46

UBS Series Funds

In determining net asset value, each of GovernmentMaster Fund and Treasury Master Fund values itssecurities at their amortized cost (unless the fund’sboard (or its delegate) determines that this does notrepresent fair value), and each of UBS Select Gov-ernment Preferred Fund and UBS Select TreasuryPreferred Fund buys the corresponding masterfund’s interests at the master fund’s net assetvalue. The amortized cost method uses a constantamortization to maturity of the difference betweenthe cost of the instrument to a fund and theamount due at maturity. The net asset value pershare of each of UBS Select Government PreferredFund and UBS Select Treasury Preferred Fund isexpected to be $1.00, although this value is notguaranteed.

In determining net asset value, each of PrimeMaster Fund and ESG Prime Master Fund values itssecurities using market-based values (unless thefund’s board (or its delegate) determines that thisdoes not represent fair value), and each of UBSSelect Prime Preferred Fund and UBS Select ESGPrime Preferred Fund buys the relevant masterfund’s interests at the master fund’s net assetvalue. The net asset value per share of each of UBSSelect Prime Preferred Fund and UBS Select ESGPrime Preferred Fund is calculated to four decimals(e.g., $1.0000) and will fluctuate.

The net asset value per share of each of UBS SelectGovernment Preferred Fund and UBS Select Trea-sury Preferred Fund is normally determined ninetimes each business day, every hour on the hour,beginning at 9:00 a.m. (Eastern time) and conclud-ing at 5:00 p.m. (Eastern time). The net asset valueper share of each of UBS Select Prime PreferredFund and UBS Select ESG Prime Preferred Fund isnormally determined three times each business day,at 8:00 a.m. (Eastern time), 12:00 noon (Easterntime) and 3:00 p.m. (Eastern time).

Your price for buying or selling shares will be basedupon the net asset value that is next calculatedafter the fund receives your order.

On any day that a fund determines to advance thetime by which orders to buy or sell its shares mustbe received by the transfer agent as describedabove under “Buying shares,” the time for determi-nation of the fund’s net asset value per share willbe as of the same time the fund has determined tocease accepting orders to buy or sell its shares. Thefund will not price its shares again on that businessday even though it normally prices its shares morefrequently.

The funds’ board has delegated to a UBS AM valua-tion committee the responsibility for making fairvalue determinations with respect to a fund’s port-folio securities. The types of securities and otherinstruments for which such fair value pricing maybe necessary include, but are not limited to: securi-ties of an issuer that has entered into a restructur-ing; fixed-income securities that have gone intodefault and for which there is no current marketvalue quotation; Section 4(a)(2) commercial paper;securities or instruments that are restricted as totransfer or resale; illiquid instruments; and instru-ments for which the prices or values available donot, in the judgment of UBS AM, represent currentmarket value. The need to fair value a fund’s port-folio securities may also result from low trading vol-ume in foreign markets or thinly traded securities orinstruments. Various factors may be reviewed inorder to make a good faith determination of asecurity’s or instrument’s fair value. These factorsinclude, but are not limited to, fundamental analyti-cal data relating to the investment; the nature andduration of restrictions on disposition of the securi-ties or instruments; and the evaluation of forceswhich influence the market in which the securitiesor instruments are purchased and sold.

47

UBS Series Funds

Each fund’s portfolio holding consists of an interestin the master fund in which the fund invests. Thevalue of such portfolio holding reflects each fund’sproportionate interest in the net assets of its corre-sponding master fund. Each master fund generallyvalues securities and other instruments in a manneras described in that master fund’s prospectus orsimilar document.

ManagementInvestment advisorUBS Asset Management (Americas) Inc. (“UBSAM”) acts as the investment advisor and adminis-trator for Prime Master Fund, ESG Prime MasterFund, Government Master Fund and TreasuryMaster Fund, which are the master funds in whichthe funds invest their assets. UBS AM also acts asthe administrator for the funds. As investment advi-sor, UBS AM makes the master funds’ investmentdecisions. It buys and sells securities for the masterfunds and conducts the research that leads to thepurchase and sale decisions.

UBS AM is a Delaware corporation with its principalbusiness offices located at One North Wacker Drive,Chicago, IL 60606 and at 1285 Avenue of theAmericas, New York, New York, 10019-6028. UBSAM is an investment adviser registered with the SEC.UBS AM is an indirect asset management subsidiaryof UBS Group AG (“UBS”). As of September 30,2019, UBS AM had approximately $199.0 billion inassets under management. UBS AM is a member ofthe UBS Asset Management Division, which hadapproximately $858.0 billion in assets under man-agement world-wide as of September 30, 2019. UBSis an internationally diversified organization head-quartered in Zurich, Switzerland and with operationsin many areas of the financial services group ofindustries.

Advisory and administration feesUBS AM’s contract fee for the advisory and admin-istrative services it provides to each master fund isbased on the following fee schedule:

$0 – $30 billion . . . . . . . . . . . . . . . . . . . 0.1000%Above $30 billion up to $40 billion . . . . 0.0975%Above $40 billion up to $50 billion . . . . 0.0950%Above $50 billion up to $60 billion . . . . 0.0925%Above $60 billion . . . . . . . . . . . . . . . . . . 0.0900%

UBS AM’s contract fee for the administrative ser-vices it provides to each feeder fund is 0.08% ofeach feeder fund’s average daily net assets.

In exchange for these fees, UBS AM has agreed tobear all of the funds’ expenses other than interest,taxes, extraordinary costs and the cost of securitiespurchased and sold by the funds, including anytransaction costs. Although UBS AM is not obli-gated to pay the fees and expenses of the funds’independent trustees, it is contractually obligated toreduce its management fee in an amount equal tothose fees and expenses. UBS AM estimates thatthese fees and expenses will be less than 0.01% ofeach fund’s average daily net assets.

UBS AM received an effective fee of 0.12%, 0.14%and 0.14% of the average daily net assets of eachof UBS Select Prime Preferred Fund, UBS SelectGovernment Preferred Fund and UBS Select Trea-sury Preferred Fund, respectively, for its services asinvestment advisor and administrator in the funds’last fiscal year which ended April 30, 2019 (includesfees allocated from related master fund, net of feewaivers/expense reimbursements, if any). These feesreflect fee waivers pursuant to a fee waiver agree-ment (as well as additional voluntary fee waiverswith respect to UBS Select Prime Preferred Fund).With respect to UBS Select ESG Prime PreferredFund, UBS AM did not receive any fees for itsservices as investment advisor and administrator for

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UBS Series Funds

the last fiscal year as the fund had not yet com-menced operations as of April 30, 2019.

UBS AM will voluntarily waive its 0.10% masterfund level fee in order to voluntarily reduce UBSSelect ESG Prime Preferred Fund’s expenses by0.10% until April 30, 2020. This voluntary feewaiver is in addition to the contractual fee waiverarrangement that caps the fund’s ordinary operat-ing expenses at 0.14% through December 31,2020, as described in the “Fund summary” above.UBS AM may further voluntarily waive fees fromtime to time. For example, UBS AM may voluntarilyundertake to waive fees in the event that fundyields drop below a certain level. Once started,there is no guarantee that UBS AM would continueto voluntarily waive a portion of its fees. Waiversmay impact a fund’s performance.

A discussion regarding the basis for the masterfunds’ board’s approval of the Management Agree-ment between UBS AM and Master Trust withrespect to Prime Master Fund, Government MasterFund and Treasury Master Fund is available in thefunds’ semiannual report to shareholders for thefiscal period ended October 31, 2018. A discussionregarding the basis of the board’s approval of theManagement Agreement between UBS AM andMaster Trust with respect to ESG Prime MasterFund is expected to be available in the funds’annual report to shareholders for the fiscal periodended April 30, 2020.

Master-feeder structureUBS Select Prime Preferred Fund, UBS Select Gov-ernment Preferred Fund, UBS Select Treasury Pre-ferred Fund and UBS Select ESG Prime PreferredFund are “feeder funds” that invest all of theirassets in “master funds”—Prime Master Fund, Gov-ernment Master Fund, Treasury Master Fund andESG Prime Master Fund, respectively. The feeder

funds and their respective master funds have thesame investment objectives.

The master funds may accept investments fromother feeder funds. Each feeder fund bears themaster fund’s expenses in proportion to theirinvestment in the master fund. Each feeder fund canset its own transaction minimums, feeder fund-specific expenses and other conditions. Thisarrangement allows each feeder fund’s trustees towithdraw the feeder fund’s assets from the masterfund if they believe doing so is in the shareholders’best interests. If the trustees withdraw the feederfund’s assets, they would then consider whether thefeeder fund should hire its own investment advisor,invest in a different master fund or take other action.

Other informationTo the extent authorized by law, each fund reservesthe right to discontinue offering shares at any time,merge, reorganize itself or cease operations andliquidate.

Dividends and taxesDividendsEach fund declares dividends daily and pays themmonthly. Dividends accrued during a given monthare paid on the first business day of the next monthor upon the sale of all the fund shares in a share-holder’s account.

Each fund may distribute all or a portion of its capi-tal gains (if any) to the extent required to ensurethat the fund maintains its federal tax law status asa regulated investment company. Each of UBSSelect Government Preferred Fund and UBS SelectTreasury Preferred Fund will also distribute all or aportion of its capital gains to the extent necessaryto maintain its share price at $1.00.

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UBS Series Funds

Shares of each fund earn dividends on the day theyare purchased but do not earn dividends on the daythey are sold.

You will receive dividends in additional sharesunless you elect to receive them in cash. If you pre-fer to receive dividends in cash, contact your Finan-cial Advisor (if you purchased your shares through afinancial intermediary) or the transfer agent (if youpurchased your shares directly).

While each fund declares dividends daily and paysthem monthly, the amounts are rounded to thenearest $0.01 on a daily basis with respect to eachinvestor’s fund account. As a result, investorswhose fund account balances earn daily dividendsthat total less than one half a cent on any given daywill not accrue any dividends on that day.

TaxesThe dividends that you receive from the funds gen-erally are subject to federal income tax regardless ofwhether you receive them in additional fund sharesor in cash, and are expected to be taxed as ordinaryincome. Such dividends are not eligible for thereduced rate of tax that may apply to certain quali-fying dividends on corporate stock. Dividends paidby the funds are also not expected to qualify as“exempt-interest dividends,” and will not beexcludable from gross income by shareholders,because each fund is not expected to invest at least50% of the value of its total assets in securities theinterest on which is excludable from gross income.

Although dividends are generally treated as taxableto you in the year they are paid, dividends declared inOctober, November or December but paid inJanuary are taxable as if they were paid in December.

Shareholders not subject to tax on their income willnot be required to pay tax on amounts distributed

to them. If you hold fund shares through a tax-exempt account or plan such as an IRA or401(k) plan, dividends on your shares generally willnot be subject to tax until proceeds are withdrawnfrom the plan.

Some states and localities do not tax dividends thatare attributable to interest on certain governmentsecurities under certain circumstances. However,these dividends may be subject to corporate fran-chise tax in some states.

Each fund will tell you annually the character of div-idends for tax reporting purposes. You will gener-ally not recognize any gain or loss on the sale orexchange of your fund shares as long as the fundmaintains a share price of $1.00.

A liquidity fee imposed by a fund will reduce theamount you will receive upon the redemption ofyour shares, and will decrease the amount of anycapital gain or increase the amount of any capitalloss you will recognize from such redemption. Thereis some degree of uncertainty with respect to thetax treatment of liquidity fees received by moneymarket funds, and such tax treatment may be thesubject of future guidance issued by the InternalRevenue Service (“IRS”). If a fund receives liquidityfees, it will consider the appropriate tax treatmentof such fees to the fund at such time.

Because neither of UBS Select Prime Preferred Fundnor UBS Select ESG Prime Preferred Fund maintain astable share price, a sale or exchange of fund sharesmay result in a capital gain or loss for you. Unlessyou choose to adopt a simplified “NAV method” ofaccounting (described below), such capital gain orloss generally will be treated either as short-term ifyou held your shares as capital assets for one year orless, or long-term if you held your shares longer. Indetermining the holding period of such shares for

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UBS Series Funds

this purpose, any period during which your risk ofloss is offset by means of options, short sales or simi-lar transactions is not counted.

If you elect to adopt the NAV method of accounting,rather than computing gain or loss on every taxabledisposition of UBS Select Prime Preferred Fund andUBS Select ESG Prime Preferred Fund shares asdescribed above, you would determine your gain orloss based on the change in the aggregate value ofyour shares during a computation period (such asyour taxable year), reduced by your net investment(purchases minus sales) in those shares during thatperiod. Under the NAV method, any resulting netcapital gain or loss would be treated as short-termcapital gain or loss, provided that you held the sharesas capital assets. The IRS has issued guidance indicat-ing that wash sale rules will not apply to taxpayerswith respect to shares redeemed from a floating netasset value money market fund, such as UBS SelectPrime Preferred Fund and UBS Select ESG Prime Pre-ferred Fund.

An additional 3.8% Medicare tax is imposed oncertain net investment income (including ordinarydividends and capital gain distributions receivedfrom a fund and net gains from redemptions orother taxable dispositions of fund shares) of USindividuals, estates and trusts to the extent thatsuch person’s “modified adjusted gross income” (inthe case of an individual) or “adjusted grossincome” (in the case of an estate or trust) exceedscertain threshold amounts.

Each fund may be required to withhold a 24%federal tax on all dividends payable to you

• if you fail to provide the fund or UBS Financial Ser-vices Inc. with your correct taxpayer identificationnumber on Form W-9 (for US citizens and residentaliens) or to make required certifications, or

• if you have been notified by the IRS that you aresubject to backup withholding.

Taxable distributions to non-residents will generallybe subject to a 30% withholding tax (or lowerapplicable treaty rate).

Each fund is required to withhold US tax (at a 30%rate) on payments of taxable dividends made to cer-tain non-US entities that fail to comply (or bedeemed compliant) with extensive new reportingand withholding requirements designed to informthe US Department of the Treasury of US-owned for-eign investment accounts. Shareholders may berequested to provide additional information to thefunds to enable the funds to determine whetherwithholding is required.

The above is a general and abbreviated discussion ofcertain tax considerations, and each investor is advisedto consult with his or her own tax advisor. There isadditional information on taxes in the funds’ SAI.

Disclosure of portfolioholdings and otherinformationEach fund is a “feeder fund” that invests in securi-ties through an underlying master fund. Each fundand the corresponding master fund have the sameinvestment objective.

Each fund’s complete schedule of portfolio holdingsfor the second and fourth quarters of each fiscalyear will be included in its semiannual and annualreports to shareholders and is filed with the SEC onForm N-CSR. Each fund’s Forms N-CSR are availableon the SEC’s website at http://www.sec.gov. Addi-tionally, you may obtain copies of semiannual and

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UBS Series Funds

annual reports to shareholders from the funds uponrequest by calling 1-800-647 1568. The semiannualand annual reports for each fund will be posted onthe fund’s website athttps://www.ubs.com/usmoneymarketfunds.

Each fund will disclose on UBS AM’s website,within five business days after the end of eachmonth, a complete schedule of the related masterfund’s portfolio holdings and information regardingthe weighted average maturity and weighted aver-age life of such master fund. This information willbe posted on the UBS website at the followinginternet address:https://www.ubs.com/usmoneymarketfunds. Inaddition, each fund will file with the SEC onForm N-MFP, within five business days after the endof each month, more detailed portfolio holdingsinformation. Each fund’s Forms N-MFP will be avail-able on the SEC’s website; UBS AM’s website willalso contain a link to these filings. The UBS AMwebsite will also disclose the following informationfor each fund as of the end of each business dayfor the previous six months: (1) the percentage ofeach fund’s total assets invested in daily and weeklyliquid assets; (2) each fund’s daily net inflows andoutflows; and (3) each fund’s current market-basednet asset value per share to four decimal places,which is calculated using current market quotations(or an appropriate substitute that reflects currentmarket conditions). ( For purposes of transactions inthe shares of UBS Select Treasury Preferred Fundand UBS Select Government Preferred Fund, theprice for shares will be the net asset value pershare, calculated using the amortized cost methodto two decimal places as further described in thisprospectus and the related SAI.) Investors also mayfind additional information about each fund at theabove referenced UBS website internet address.

Additionally, an abbreviated portfolio holdingsreport for each of the master funds in which UBSSelect Prime Preferred Fund and UBS Select ESGPrime Preferred Fund invests is available on aweekly basis. (The abbreviated weekly portfolioholdings report contains less information abouteach holding.) This information will be posted onthe UBS website at the following internet address:https://www.ubs.com/usmoneymarketfunds. Undernormal circumstances, the abbreviated report willbe as of the last business day in a week and isexpected to be posted by the Thursday or Friday ofthe following week. The weekly information will beposted to the website at least one day prior toother public dissemination.

The weekly portfolio holdings information postingswill continue to remain available on the website,along with any more current holdings information, atleast until the date on which a fund files its portfolioholdings information with the SEC on Forms N-CSRfor the period that included the date as of which thewebsite information is current. (For example, a fundfiles its annual report for its most recent fiscal yearended April 30th with the SEC on Form N-CSR aroundthe beginning of July. Weekly portfolio holdings infor-mation for periods ended April 30th could be re-moved from the website once the annual report isfiled, but not until then.)

Please consult the funds’ SAI for a description ofthe policies and procedures that govern disclosureof the funds’ portfolio holdings.

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UBS Series Funds

Financial highlights

The following financial highlights tables areintended to help you understand the financial per-formance for UBS Select Prime Preferred Fund andUBS Select Treasury Preferred Fund for the past fiveyears and for UBS Select Government PreferredFund since it commenced operations on June 28,2016 through April 30, 2019.

No financial highlights are shown for UBS SelectESG Prime Preferred Fund, which had not com-menced operations as of April 30, 2019.

Certain information reflects financial results for a sin-gle fund share. In the tables, “total investment

return” represents the rate that an investor wouldhave earned on an investment in a fund (assumingreinvestment of all dividends and other distributions).

The information in the financial highlights has beenderived from the financial statements audited byErnst & Young LLP, an independent registered pub-lic accounting firm, whose report appears in theAnnual Report to Shareholders of the relevantfunds. You may obtain copies of the funds’ AnnualReport without charge by calling 1-888-547 FUND.

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UBS Series Funds: UBS Select Prime Preferred Fund

Financial highlights (continued)

Selected data for a share of beneficial interest outstanding throughout each year is presented below:

Years ended April 30,

2019 2018 2017 2016 2015

Net asset value, beginning of year $ 1.0001 $ 1.0002 $ 1.0000 $ 1.00 $ 1.00

Net investment income 0.0226 0.0137 0.0061 0.002 0.001Net realized and unrealized gain (loss) 0.00002 (0.0001) 0.0011 0.0001 0.0001

Net increase from operations 0.0226 0.0136 0.0072 0.002 0.001

Dividends from net investment income (0.0226) (0.0137) (0.0061) (0.002) (0.001)Distributions from net realized gain (0.0000)2 (0.0000)2 (0.0009) (0.000)1 (0.000)1

Total dividends and distributions (0.0226) (0.0137) (0.0070) (0.002) (0.001)

Net asset value, end of year $ 1.0001 $ 1.0001 $ 1.0002 $ 1.00 $ 1.00

Total investment return3 2.28% 1.37% 0.72% 0.21% 0.07%

Ratios to average net assets:Expenses before fee waivers4 0.18% 0.18% 0.18% 0.18% 0.18%Expenses after fee waivers4 0.12% 0.08% 0.13% 0.14% 0.14%Net investment income4 2.29% 1.40% 0.44% 0.21% 0.07%

Supplemental data:Net assets, end of year (000’s) $2,751,367 $1,732,540 $599,760 $7,187,548 $5,349,181

1 Amount represents less than $0.0005 per share.2 Amount represents less than $0.00005 per share.3 Total investment return is calculated assuming a $10,000 investment on the first day of each year reported, reinvestment of all dividends and other distri-

butions, if any, at net asset value on the payable dates, and a sale at net asset value on the last day of each year reported. Returns do not reflect thededuction of taxes that a shareholder would pay on fund distributions.

4 Ratios include the fund’s share of income, expenses and expense waivers allocated from the Master Fund.

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UBS Series Funds: UBS Select Government Preferred Fund

Financial highlights (continued)

Selected data for a share of beneficial interest outstanding throughout each period is presented below:

Years ended April 30,For the period from

June 28, 20161 toApril 30, 20172019 2018

Net asset value, beginning of period $ 1.00 $ 1.00 $ 1.00

Net investment income 0.020 0.010 0.003Net realized gain (loss) 0.0002 (0.000)2 0.0002

Net increase from operations 0.020 0.010 0.003

Dividends from net investment income (0.020) (0.010) (0.003)Distributions from net realized gain — (0.000)2 (0.000)2

Total dividends and distributions (0.020) (0.010) (0.003)

Net asset value, end of period $ 1.00 $ 1.00 $ 1.00

Total investment return3 2.05% 1.04% 0.34%

Ratios to average net assets:Expenses before fee waivers4 0.18% 0.18% 0.18%5

Expenses after fee waivers4 0.14% 0.14% 0.09%5

Net investment income4 2.03% 1.03% 0.47%5

Supplemental data:Net assets, end of period (000’s) $3,609,757 $3,913,629 $4,098,750

1 Commencement of operations.2 Amount represents less than $0.0005 per share.3 Total investment return is calculated assuming a $10,000 investment on the first day of each period reported, reinvestment of all dividends and other dis-

tributions, if any, at net asset value on the payable dates, and a sale at net asset value on the last day of each period reported. Total investment return forthe period of less than one year has not been annualized. Returns do not reflect the deduction of taxes that a shareholder would pay on fund distributions.

4 Ratios include the fund’s share of income, expenses and expense waivers allocated from the Master Fund.5 Annualized.

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UBS Series Funds: UBS Select Treasury Preferred Fund

Financial highlights (concluded)

Selected data for a share of beneficial interest outstanding throughout each year is presented below:

Years ended April 30,

2019 2018 2017 2016 2015

Net asset value, beginning of year $ 1.00 $ 1.00 $ 1.00 $ 1.00 $ 1.00

Net investment income 0.020 0.010 0.003 0.001 0.0001

Net realized gain 0.0001 0.0001 0.0001 0.0001 0.0001

Net increase from operations 0.020 0.010 0.003 0.001 0.0001

Dividends from net investment income (0.020) (0.010) (0.003) (0.001) (0.000)1

Distributions from net realized gain (0.000)1 (0.000)1 (0.000)1 (0.000)1 (0.000)1

Total dividends and distributions (0.020) (0.010) (0.003) (0.001) (0.000)1

Net asset value, end of year $ 1.00 $ 1.00 $ 1.00 $ 1.00 $ 1.00

Total investment return2 2.06% 1.04% 0.34% 0.07% 0.01%

Ratios to average net assets:Expenses before fee waivers3 0.18% 0.18% 0.18% 0.18% 0.18%Expenses after fee waivers3 0.14% 0.14% 0.14% 0.10% 0.06%Net investment income3 2.00% 1.04% 0.36% 0.06% 0.01%

Supplemental data:Net assets, end of year (000’s) $5,627,247 $9,248,153 $10,356,105 $4,993,806 $4,594,241

1 Amount represents less than $0.0005 per share.2 Total investment return is calculated assuming a $10,000 investment on the first day of each year reported, reinvestment of all dividends and other distri-

butions, if any, at net asset value on the payable dates, and a sale at net asset value on the last day of each year reported. Returns do not reflect thededuction of taxes that a shareholder would pay on fund distributions.

3 Ratios include the fund’s share of income, expenses and expense waivers allocated from the Master Fund.

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UBS Series Funds: Appendix A

Additional information regarding purchases and redemptions

The funds are open for business each day that the Federal Reserve Bank of New York, the New York StockExchange (“NYSE”) and the principal bond markets (as recommended by the Securities Industry and Finan-cial Markets Association (“SIFMA”)) are open. One or more of these will be closed on the observance ofthe holidays listed below. In addition, UBS Select Government Preferred Fund and UBS Select Treasury Pre-ferred Fund will advance the final time by which orders to buy or sell shares must be received by the trans-fer agent to 3:00 p.m. (Eastern time) on those days that SIFMA has recommended that the bond marketsclose early. The normal deadline by which orders to buy or sell shares of UBS Select Prime Preferred Fundand UBS Select ESG Prime Preferred Fund must be received by the transfer agent is 3:00 p.m. (Easterntime). Those days SIFMA has recommended that the bond markets close early remaining through 2019and for 2020 are listed below.

Holidays (observed) Early closeNew Year’s Day (January 1, 2020) December 31, 2019Martin Luther King Day (January 20, 2020) —Presidents Day (February 17, 2020) —Good Friday (April 10, 2020) April 9, 2020Memorial Day (May 25, 2020) May 22, 2020Independence Day (July 4, 2020) July 3, 2020Labor Day (September 7, 2020) —Columbus Day (October 12, 2020) —Veterans Day (November 11, 2020) —Thanksgiving Day (November 26, 2020) November 27, 2020Christmas Day (December 25, 2020) December 24, 2020

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UBS Series Funds

Privacy notice

UBS family of funds privacy notice

This notice describes the privacy policy of the UBS Family of Funds and the PACE® Funds managed by UBSAsset Management (collectively, the "Funds"). The Funds are committed to protecting the personal infor-mation that they collect about individuals who are prospective, current or former investors.

The Funds collect personal information in order to process requests and transactions and to provide cus-tomer service. Personal information, which is obtained from applications and other forms or correspon-dence submitted to the Funds, may include name(s), address, e-mail address, telephone number, date ofbirth, social security number or other tax identification number, bank account information, informationabout your transactions and experiences with the Funds, and any affiliation a client has with UBS FinancialServices Inc. or its affiliates ("Personal Information").

The Funds limit access to Personal Information to those individuals who need to know that information inorder to process transactions and service accounts. These individuals are required to maintain and protectthe confidentiality of Personal Information and to follow established procedures. The Funds maintain phys-ical, electronic and procedural safeguards to protect Personal Information and to comply with applicablelaws and regulations.

The Funds may share Personal Information with their affiliates to facilitate the servicing of accounts and forother business purposes, or as otherwise required or permitted by applicable law. The Funds may alsoshare Personal Information with non-affiliated third parties that perform services for the Funds, such asvendors that provide data or transaction processing, computer software maintenance and development,and other administrative services. When the Funds share Personal Information with a non-affiliated thirdparty, they will do so pursuant to a contract that includes provisions designed to ensure that the thirdparty will uphold and maintain privacy standards when handling Personal Information. In addition to shar-ing information with non-affiliated third parties to facilitate the servicing of accounts and for other busi-ness purposes, the Funds may disclose Personal Information to non-affiliated third parties as otherwiserequired or permitted by applicable law. For example, the Funds may disclose Personal Information tocredit bureaus or regulatory authorities to facilitate or comply with investigations; to protect against orprevent actual or potential fraud, unauthorized transactions, claims or other liabilities; or to respond tojudicial or legal process, such as subpoena requests.

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UBS Series Funds

Except as described in this privacy notice, the Funds will not use Personal Information for any other pur-pose unless the Funds describe how such Personal Information will be used and clients are given an oppor-tunity to decline approval of such use of Personal Information relating to them (or affirmatively approvethe use of Personal Information, if required by applicable law). The Funds endeavor to keep their customerfiles complete and accurate. The Funds should be notified if any Personal Information needs to be cor-rected or updated. Please call 1-800-647 1568 with any questions or concerns regarding your PersonalInformation or this privacy notice.

This privacy notice is not a part of the prospectus.

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UBS Series Funds

UBS Asset Management, Americas Region

Business continuity planning overview

UBS Asset Management affiliates UBS Asset Management (US) Inc. and UBS Asset Management(Americas) Inc. protect information assets, processes, and customer data from unpredictable eventsthrough preparation and testing of a comprehensive business continuity capability. This capability seeksrecovery of the technology infrastructure and information, and prevention of the loss of company or cus-tomer information and transactions. In the event of a crisis scenario, we will recover those functionsdeemed to be critical to our business and our clients, and strive to resume processing within predefinedtime frames following a disaster declaration (typically 4-6 hours). Business continuity processes provide usthe ability to continue critical business functions regardless of the type, scope, or duration of a localizedevent. However, these processes are dependent upon various external resources, such as regional telecom-munications, transportation networks, and other public utilities.

Essential elements of the business continuity plan include:

• Crisis communication procedures—Action plans for coordinating essential communications for crisismanagement leaders, employees, and key business partners

• Information technology backup and recovery procedures—Comprehensive technology and datamanagement plans designed to protect the integrity and quick recovery of essential technology infra-structure and data

• Disaster recovery site—Alternative dedicated workspace, technology infrastructure, and systems sup-port that is fully operational during a disaster declaration

• Testing regimen—The business continuity plan is reviewed on an annual basis, including the disasterrecovery facility. In addition, all IT application recovery plans are updated and tested annually.

This business continuity planning overview is not a part of the prospectus.

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If you want more information about the funds, the followingdocuments are available free of charge upon request:

Annual/semiannual reportsAdditional information about each fund’s investments is availablein the fund’s annual and semiannual reports to shareholders.

Statement of Additional Information (SAI)The funds’ SAI provides more detailed information about thefunds and is incorporated by reference into this prospectus (i.e., itis legally a part of this prospectus).

You may discuss your questions about the funds by contactingyour Financial Advisor. You may obtain free copies of the funds’annual and semiannual reports and their SAI by contacting thefunds directly at 1-800-647 1568. The funds’ annual andsemiannual reports and their SAI will also be posted on the UBSwebsite at the following internet address:https://www.ubs.com/usmoneymarketfunds. You may also requestother information about the funds and make shareholder inquiriesvia the telephone number above.

You can get copies of reports and other information about thefunds:

• For a fee, by electronic request at [email protected]; or

• Free, from the EDGAR database on the SEC’s Internet website athttp://www.sec.gov.

UBS Series Funds—UBS Select Prime Preferred Fund—UBS Select Government Preferred Fund—UBS Select Treasury Preferred Fund—UBS Select ESG Prime Preferred FundInvestment Company Act File No. 811-08767

© UBS 2019. All rights reserved.S030

Money Market FundsProspectus | December 30, 2019

Includes:• UBS Select Prime Preferred Fund• UBS Select Government Preferred Fund• UBS Select Treasury Preferred Fund• UBS Select ESG Prime Preferred Fund

Documents

Money Market Funds · Shareholder fees (fees paid directly from your investment) Maximum front-end sales charge (load) imposed on purchases None Maximum deferred sales charge (load)