# EDGAR Filing Document

**Accession Number:** 0001060517
**File Stem:** 0001410368-26-057287
**Filing Date:** 2026-6
**Character Count:** 13632
**Document Hash:** 87cb5ea17d6b550cf8385eeec0d68dbf
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001410368-26-057287.hdr.sgml**: 20260605

**ACCESSION NUMBER**: 0001410368-26-057287

**CONFORMED SUBMISSION TYPE**: N-MFP3

**PUBLIC DOCUMENT COUNT**: 1

**CONFORMED PERIOD OF REPORT**: 20260531

**FILED AS OF DATE**: 20260605

**DATE AS OF CHANGE**: 20260605

**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:** N-MFP3
- **SEC ACT:** 1940 Act
- **SEC FILE NUMBER:** 811-08767
- **FILM NUMBER:** 261068590

**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 Preferred Fund (Series ID: S000018677)

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

# Form N-MFP3: Monthly Schedule of Portfolio Holdings

## N-MFP: Filer Information
**Submission Type:** N-MFP3
**CIK:** 0001060517

### General Information

**Report for (YYYY-MM-DD):** 2026-05-31

**Registrant Full Name:** UBS Series Funds

**CIK Number of Registrant:** 0001060517

**LEI of Registrant:** 54930058UKPXVB81RJ71

**Name of Series:** UBS Select Treasury Preferred Fund

**LEI of Series:** 549300DXQ8KM8WHPPG39

**EDGAR Series Identifier:** S000018677

**Total number of share classes in the series:** 1

**Is this the fund's final filing on Form N-MFP?:** No

**Has the fund acquired or merged with another fund?:** No

## Part A: Series-Level Information about the Fund

### Service Providers
| Role                          | Details                                                      | File/CIK Number   |
|:---|:---|:---|
| Investment Adviser            | UBS ASSET MANAGEMENT (AMERICAS) LLC                          | 801-34910         |
| Independent Public Accountant | Ernst & Young  LLP<br>City: New York<br>State: NY            |  |
| Administrator                 | UBS ASSET MANAGEMENT (AMERICAS) LLC                          |  |
| Transfer Agent                | BNY Mellon Investment Servicing (US) Inc.<br>CIK: 0000849542 | 084-01761         |

### Fund Characteristics & Assets

- **Securities Act File Number:** 333-52965

- **Is this a Feeder Fund?:** Yes

- **Is this a Master Fund?:** No

- **Is this series for insurance company separate accounts?:** No

- **Money Market Fund Category:** Government

- **Is this a Retail Money Market Fund?:** No

- **Is this a Government Money Market Fund?:** Yes

- **WAM:** 1 days

- **WAL:** 1 days

- **Total Value of Portfolio Securities:** $22923122610.92

- **Amortized Cost of Portfolio Securities:** $0.00

- **Cash:** $0.00

- **Total Other Assets:** $0.00

- **Total Liabilities:** $68012497.50

- **Net Assets of Series:** $22855110113.42

- **Number of Shares Outstanding (Series):** 22854317861.2900

- **Does the fund seek to maintain a stable price per share?:** Yes

- **Stable Price Per Share:** $1.00

- **Is cash management vehicle an affiliated fund?:** No

- **Does the fund apply liquidity fees?:** No

### Daily & Weekly Liquid Assets
| Date       | Daily Liquid Assets ($)   | Weekly Liquid Assets ($)   | Daily Liquid Assets (%)   | Weekly Liquid Assets (%)   |
|:---|:---|:---|:---|:---|
| 2026-05-01 | $39286345315.19           | $39286345315.19            | 99.9700%                  | 99.9700%                   |
| 2026-05-04 | $40363211037.65           | $40363211037.65            | 99.9800%                  | 99.9800%                   |
| 2026-05-05 | $40239253920.41           | $40239253920.41            | 99.9800%                  | 99.9800%                   |
| 2026-05-06 | $40296766955.68           | $40296766955.68            | 99.9800%                  | 99.9800%                   |
| 2026-05-07 | $39656472253.95           | $39656472253.95            | 99.9800%                  | 99.9800%                   |
| 2026-05-08 | $40079606482.64           | $40079606482.64            | 99.9600%                  | 99.9600%                   |
| 2026-05-11 | $41503213280.42           | $41503213280.42            | 99.9700%                  | 99.9700%                   |
| 2026-05-12 | $41121154532.34           | $41121154532.34            | 99.9700%                  | 99.9700%                   |
| 2026-05-13 | $42046230527.54           | $42046230527.54            | 99.9700%                  | 99.9700%                   |
| 2026-05-14 | $40936492153.76           | $40936492153.76            | 99.9700%                  | 99.9700%                   |
| 2026-05-15 | $41845922243.86           | $41845922243.86            | 99.9700%                  | 99.9700%                   |
| 2026-05-18 | $42732249990.27           | $42732249990.27            | 99.9700%                  | 99.9700%                   |
| 2026-05-19 | $42137119470.36           | $42137119470.36            | 99.9700%                  | 99.9700%                   |
| 2026-05-20 | $42911297663.03           | $42911297663.03            | 99.9700%                  | 99.9700%                   |
| 2026-05-21 | $42097660203.82           | $42097660203.82            | 99.9700%                  | 99.9700%                   |
| 2026-05-22 | $42398860931.06           | $42398860931.06            | 99.9600%                  | 99.9600%                   |
| 2026-05-26 | $42095943147.53           | $42095943147.53            | 99.9700%                  | 99.9700%                   |
| 2026-05-27 | $43020279600.75           | $43020279600.75            | 99.9700%                  | 99.9700%                   |
| 2026-05-28 | $41212077469.31           | $41212077469.31            | 99.9600%                  | 99.9600%                   |
| 2026-05-29 | $41089870438.24           | $41089870438.24            | 99.9500%                  | 99.9500%                   |

### 7-Day Gross Yield
| Date       | 7-Day Gross Yield   |
|:---|:---|
| 2026-05-01 | 3.7000%             |
| 2026-05-04 | 3.6900%             |
| 2026-05-05 | 3.6900%             |
| 2026-05-06 | 3.6900%             |
| 2026-05-07 | 3.6800%             |
| 2026-05-08 | 3.6800%             |
| 2026-05-11 | 3.6800%             |
| 2026-05-12 | 3.6700%             |
| 2026-05-13 | 3.6700%             |
| 2026-05-14 | 3.6700%             |
| 2026-05-15 | 3.6600%             |
| 2026-05-18 | 3.6600%             |
| 2026-05-19 | 3.6600%             |
| 2026-05-20 | 3.6500%             |
| 2026-05-21 | 3.6500%             |
| 2026-05-22 | 3.6500%             |
| 2026-05-26 | 3.6500%             |
| 2026-05-27 | 3.6600%             |
| 2026-05-28 | 3.6600%             |
| 2026-05-29 | 3.6800%             |

### Daily Net Asset Value per Share (Series)
| Date       | Net Asset Value per Share   |
|:---|:---|
| 2026-05-01 | 1.0001                      |
|  |  |
| 2026-05-04 | 1.0001                      |
|  |  |
| 2026-05-05 | 1.0001                      |
|  |  |
| 2026-05-06 | 1.0001                      |
|  |  |
| 2026-05-07 | 1.0001                      |
|  |  |
| 2026-05-08 | 1.0001                      |
|  |  |
| 2026-05-11 | 1.0001                      |
|  |  |
| 2026-05-12 | 1.0001                      |
|  |  |
| 2026-05-13 | 1.0001                      |
|  |  |
| 2026-05-14 | 1.0001                      |
|  |  |
| 2026-05-15 | 1.0001                      |
|  |  |
| 2026-05-18 | 1.0001                      |
|  |  |
| 2026-05-19 | 1.0001                      |
|  |  |
| 2026-05-20 | 1.0001                      |
|  |  |
| 2026-05-21 | 1.0001                      |
|  |  |
| 2026-05-22 | 1.0001                      |
|  |  |
| 2026-05-26 | 1.0001                      |
|  |  |
| 2026-05-27 | 1.0001                      |
|  |  |
| 2026-05-28 | 1.0001                      |
|  |  |
| 2026-05-29 | 1.0001                      |
|  |  |

## Part B: Class-Level Information about the Fund

### Class: Single Class

- **Minimum Initial Investment:** $50000000.00

- **Net Assets of Class:** $22855110113.42

- **Number of Shares Outstanding:** 22854317861.2900

- **Expense Reimbursement/Waiver:** 779422.00

**Daily Net Asset Value per Share (Class)**
| Date       | NAV per Share   |
|:---|:---|
| 2026-05-01 | 1.0001          |
|  |  |
| 2026-05-04 | 1.0001          |
|  |  |
| 2026-05-05 | 1.0001          |
|  |  |
| 2026-05-06 | 1.0001          |
|  |  |
| 2026-05-07 | 1.0001          |
|  |  |
| 2026-05-08 | 1.0001          |
|  |  |
| 2026-05-11 | 1.0001          |
|  |  |
| 2026-05-12 | 1.0001          |
|  |  |
| 2026-05-13 | 1.0001          |
|  |  |
| 2026-05-14 | 1.0001          |
|  |  |
| 2026-05-15 | 1.0001          |
|  |  |
| 2026-05-18 | 1.0001          |
|  |  |
| 2026-05-19 | 1.0001          |
|  |  |
| 2026-05-20 | 1.0001          |
|  |  |
| 2026-05-21 | 1.0001          |
|  |  |
| 2026-05-22 | 1.0001          |
|  |  |
| 2026-05-26 | 1.0001          |
|  |  |
| 2026-05-27 | 1.0001          |
|  |  |
| 2026-05-28 | 1.0001          |
|  |  |
| 2026-05-29 | 1.0001          |
|  |  |

**Daily Shareholder Flows**
| Date       | Gross Subscriptions ($)   | Gross Redemptions ($)   |
|:---|:---|:---|
| 2026-05-01 | $479800465.60             | $1674060685.14          |
| 2026-05-04 | $339339961.75             | $125753307.92           |
| 2026-05-05 | $412744033.47             | $141159004.23           |
| 2026-05-06 | $224157859.75             | $621239580.69           |
| 2026-05-07 | $404932960.91             | $312579659.85           |
| 2026-05-08 | $606866690.69             | $196114162.24           |
| 2026-05-11 | $909887415.88             | $338632744.75           |
| 2026-05-12 | $418811885.46             | $408944056.99           |
| 2026-05-13 | $657745667.33             | $154207483.76           |
| 2026-05-14 | $237716380.32             | $488413550.00           |
| 2026-05-15 | $1149383731.63            | $286098381.32           |
| 2026-05-18 | $262821713.39             | $248613849.33           |
| 2026-05-19 | $184834422.68             | $307514015.92           |
| 2026-05-20 | $597190189.96             | $185969490.62           |
| 2026-05-21 | $322935249.48             | $303822528.99           |
| 2026-05-22 | $987095794.30             | $875207306.51           |
| 2026-05-26 | $221849372.20             | $942512656.32           |
| 2026-05-27 | $961424434.77             | $433844203.41           |
| 2026-05-28 | $372076756.86             | $1495186167.71          |
| 2026-05-29 | $1027557917.25            | $1046500765.97          |

**Total Gross Subscriptions (Month):** $10779172903.68

**Total Gross Redemptions (Month):** $10586373601.67

**7-Day Net Yield (Class)**
| Date       | 7-Day Net Yield   |
|:---|:---|
| 2026-05-01 | 3.5600%           |
| 2026-05-04 | 3.5500%           |
| 2026-05-05 | 3.5500%           |
| 2026-05-06 | 3.5500%           |
| 2026-05-07 | 3.5400%           |
| 2026-05-08 | 3.5400%           |
| 2026-05-11 | 3.5400%           |
| 2026-05-12 | 3.5300%           |
| 2026-05-13 | 3.5300%           |
| 2026-05-14 | 3.5300%           |
| 2026-05-15 | 3.5200%           |
| 2026-05-18 | 3.5200%           |
| 2026-05-19 | 3.5200%           |
| 2026-05-20 | 3.5100%           |
| 2026-05-21 | 3.5100%           |
| 2026-05-22 | 3.5100%           |
| 2026-05-26 | 3.5100%           |
| 2026-05-27 | 3.5200%           |
| 2026-05-28 | 3.5300%           |
| 2026-05-29 | 3.5400%           |

**Beneficial/Record Owner Categories**
| Category                  | Other Category   | Record Owner %   | Beneficial Owner %   |
|:---|:---|:---|:---|
| Non-financial corporation |  | 9.4900%          | 0.0000%              |
| Broker-dealer             |  | 9.0200%          | 0.0000%              |
| Other                     | IND FID AS EXEC  | 7.3300%          | 0.0000%              |

## Part C: Schedule of Portfolio Securities

### Security 1: Treasury Master Fund

- **C.1 - Title:** Treasury Master Fund
- **C.6 - Investment Category:** Investment Company
- **Identifiers:** C.3 - CUSIP: 81699K911, C.3 - LEI: 549300XQ6V293JKF0677, C.5 - Other ID: 81699K911
- **C.18 - Value (incl. sponsor support):** $22923122610.92
- **C.18.a - Value (excl. sponsor support):** $22923122610.92
- **C.19 - Percentage of Net Assets:** 100.0000%
- **C.17 - Yield as of Reporting Date:** 0.0000%
- **C.11 - Maturity Date (WAM):** 2026-06-01
- **C.12 - Maturity Date (WAL):** 2026-06-01
- **C.13 - Final Legal Maturity Date:** 2026-06-01
- **Characteristics:** C.9 Eligible Security? Yes, C.14 Has Demand Feature? No, C.15 Has Guarantee? No, C.16 Has Enhancement? No, C.22 Is an Illiquid Security? No, C.20 Is a Daily Liquid Asset? Yes, C.21 Is a Weekly Liquid Asset? Yes, C.23 Categorized at Level 3? No

## N-MFP: Signatures

**Registrant:** UBS Series Funds

**Date:** 2026-06-05

**By:** /s/Rose Ann Bubloski

**Name of Signing Officer:** Rose Ann Bubloski

**Title of Signing Officer:** Vice President