# EDGAR Filing Document

**Accession Number:** 0001060517
**File Stem:** 0001193125-26-106348
**Filing Date:** 2026-3
**Character Count:** 7091
**Document Hash:** 7b5287320188f5707b96b18c31381b33
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001193125-26-106348.hdr.sgml**: 20260313

**ACCESSION NUMBER**: 0001193125-26-106348

**CONFORMED SUBMISSION TYPE**: 497

**PUBLIC DOCUMENT COUNT**: 2

**FILED AS OF DATE**: 20260313

**DATE AS OF CHANGE**: 20260313

**EFFECTIVENESS DATE**: 20260313

**FILER**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** UBS Series Funds
- **CENTRAL INDEX KEY:** 0001060517

**ORGANIZATION NAME:**
- **EIN:** 134010447
- **STATE OF INCORPORATION:** DE
- **FISCAL YEAR END:** 0430

**FILING VALUES:**
- **FORM TYPE:** 497
- **SEC ACT:** 1933 Act
- **SEC FILE NUMBER:** 333-52965
- **FILM NUMBER:** 26753268

**BUSINESS ADDRESS:**
- **STREET 1:** C/O UBS ASSET MANAGEMENT (AMERICAS) LLC
- **STREET 2:** 1285 AVENUE OF THE AMERICAS
- **CITY:** NEW YORK
- **STATE:** NY
- **ZIP:** 10019
- **BUSINESS PHONE:** 212-821-3000

**MAIL ADDRESS:**
- **STREET 1:** C/O UBS ASSET MANAGEMENT (AMERICAS) LLC
- **STREET 2:** 1285 AVENUE OF THE AMERICAS
- **CITY:** NEW YORK
- **STATE:** NY
- **ZIP:** 10019

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** UBS MONEY SERIES
- **DATE OF NAME CHANGE:** 20020716

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** BRINSON MONEY SERIES
- **DATE OF NAME CHANGE:** 20010625

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** MITCHELL HUTCHINS LIR MONEY SERIES
- **DATE OF NAME CHANGE:** 19990730

## Series and Classes Contracts Data

### UBS Select Treasury Institutional Fund (Series ID: S000002682)

---

|  |  |  |
|:---|:---|:---|
| Class Name                             | Ticker Symbol | Class ID   |
| UBS Select Treasury Institutional Fund | SETXX         | C000007334 |

---

### UBS Select Treasury Preferred Fund (Series ID: S000018677)

---

|  |  |  |
|:---|:---|:---|
| Class Name                         | Ticker Symbol | Class ID   |
| UBS Select Treasury Preferred Fund | STPXX         | C000051800 |

---

### UBS Prime Reserves Fund (Series ID: S000052306)

---

|  |  |  |
|:---|:---|:---|
| Class Name              | Ticker Symbol | Class ID   |
| UBS Prime Reserves Fund | UPRXX         | C000164452 |

---

### UBS Prime Preferred Fund (Series ID: S000052307)

---

|  |  |  |
|:---|:---|:---|
| Class Name               | Ticker Symbol | Class ID   |
| UBS Prime Preferred Fund | UPPXX         | C000164453 |

---

### UBS Select Government Institutional Fund (Series ID: S000053131)

---

|  |  |  |
|:---|:---|:---|
| Class Name                               | Ticker Symbol | Class ID   |
| UBS Select Government Institutional Fund | SEGXX         | C000167199 |

---

### UBS Select Government Preferred Fund (Series ID: S000053132)

---

|  |  |  |
|:---|:---|:---|
| Class Name                           | Ticker Symbol | Class ID   |
| UBS Select Government Preferred Fund | SGPXX         | C000167200 |

---

### UBS Select 100% US Treasury Institutional Fund (Series ID: S000084282)

---

|  |  |  |
|:---|:---|:---|
| Class Name           | Ticker Symbol | Class ID   |
| Institutional Shares | SIOXX         | C000248579 |
| Token-Enabled Shares | TOKXX         | C000271489 |

---

### UBS Select 100% US Treasury Preferred Fund (Series ID: S000084283)

---

|  |  |  |
|:---|:---|:---|
| Class Name | Ticker Symbol | Class ID   |
| Class P    | STAXX         | C000248580 |
| Class T    | SOPXX         | C000250059 |

---

## Series and Classes Contracts Data

### UBS Select Treasury Institutional Fund (Series ID: S000002682)

| Class ID   | Class Name                             | Ticker Symbol   |
|:---|:---|:---|
| C000007334 | UBS Select Treasury Institutional Fund | SETXX           |

### UBS Select Treasury Preferred Fund (Series ID: S000018677)

| Class ID   | Class Name                         | Ticker Symbol   |
|:---|:---|:---|
| C000051800 | UBS Select Treasury Preferred Fund | STPXX           |

### UBS Prime Reserves Fund (Series ID: S000052306)

| Class ID   | Class Name              | Ticker Symbol   |
|:---|:---|:---|
| C000164452 | UBS Prime Reserves Fund | UPRXX           |

### UBS Prime Preferred Fund (Series ID: S000052307)

| Class ID   | Class Name               | Ticker Symbol   |
|:---|:---|:---|
| C000164453 | UBS Prime Preferred Fund | UPPXX           |

### UBS Select Government Institutional Fund (Series ID: S000053131)

| Class ID   | Class Name                               | Ticker Symbol   |
|:---|:---|:---|
| C000167199 | UBS Select Government Institutional Fund | SEGXX           |

### UBS Select Government Preferred Fund (Series ID: S000053132)

| Class ID   | Class Name                           | Ticker Symbol   |
|:---|:---|:---|
| C000167200 | UBS Select Government Preferred Fund | SGPXX           |

### UBS Select 100% US Treasury Institutional Fund (Series ID: S000084282)

| Class ID   | Class Name           | Ticker Symbol   |
|:---|:---|:---|
| C000248579 | Institutional Shares | SIOXX           |
| C000271489 | Token-Enabled Shares | TOKXX           |

### UBS Select 100% US Treasury Preferred Fund (Series ID: S000084283)

| Class ID   | Class Name   | Ticker Symbol   |
|:---|:---|:---|
| C000248580 | Class P      | STAXX           |
| C000250059 | Class T      | SOPXX           |

![LOGO](g92691g00s01.jpg)

March 13, 2026

**Supplement to the prospectuses (each, a "Prospectus" and together, the "Prospectuses") and Part Bs referenced on the reverse, as may have been supplemented.** 

**Includes:** 

• UBS Series Funds

• Master Trust

Dear Investor,

The purpose of this supplement is to update certain information in the Prospectuses and Part Bs, as applicable, for the above-named investment trusts, including each series thereof referenced on the reverse (collectively, the "funds"), as described below.

**The funds, indicated on the reverse chart, will be closed for business on April 3, 2026, in observance of Good Friday, in accordance with the New York Stock Exchange holiday schedule.** 

**PLEASE BE SURE TO RETAIN THIS IMPORTANT INFORMATION FOR FUTURE REFERENCE.**© UBS 2026. All rights reserved.

UBS Asset Management (Americas) LLC

ZS-1296

------

**This supplement relates to each of the following Prospectuses/Part Bs:** 

---

| | |
|:---|:---|
| **Prospectus/Part B** | **Date of<br>Prospectus/Part B** |
| **UBS Series Funds—**UBS Select Government Institutional Fund, UBS Select Treasury Institutional Fund, UBS Select 100% US Treasury Institutional Fund (Institutional Shares) | August 28, 2025 |
| **UBS Series Funds—**UBS Select 100% US Treasury Institutional Fund (Token-Enabled Shares) | January 26, 2026 |
| **UBS Series Funds—**UBS Select Government Preferred Fund, UBS Select Treasury Preferred Fund, UBS Select 100% US Treasury Preferred Fund | August 28, 2025 |
| **UBS Series Funds—**UBS Prime Preferred Fund | August 28, 2025 |
| **UBS Series Funds—**UBS Prime Reserves Fund | August 28, 2025 |
| **UBS Series Funds—**Limited Purpose Cash Investment Fund | August 22, 2025,<br>as revised<br>November 14, 2025 |
| **Master Trust—**Government Master Fund, Treasury Master Fund, 100% US Treasury Master Fund, Prime CNAV Master Fund | August 22, 2025 |

---