# EDGAR Filing Document

**Accession Number:** 0001060517
**File Stem:** 0001410368-26-000475
**Filing Date:** 2026-1
**Character Count:** 17775
**Document Hash:** 47ba0f89fac9106766ab9539e85a69a0
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001410368-26-000475.hdr.sgml**: 20260108

**ACCESSION NUMBER**: 0001410368-26-000475

**CONFORMED SUBMISSION TYPE**: N-MFP3

**PUBLIC DOCUMENT COUNT**: 1

**CONFORMED PERIOD OF REPORT**: 20251231

**FILED AS OF DATE**: 20260108

**DATE AS OF CHANGE**: 20260108

**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:** 26520439

**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 100% US Treasury Preferred Fund (Series ID: S000084283)

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

# 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):** 2025-12-31

**Registrant Full Name:** UBS Series Funds

**CIK Number of Registrant:** 0001060517

**LEI of Registrant:** 54930058UKPXVB81RJ71

**Name of Series:** UBS Select 100% US Treasury Preferred Fund

**LEI of Series:** 529900FTKZBAKZ4ON106

**EDGAR Series Identifier:** S000084283

**Total number of share classes in the series:** 2

**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:** $8989279027.90

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

- **Cash:** $0.00

- **Total Other Assets:** $55841.77

- **Total Liabilities:** $27865009.72

- **Net Assets of Series:** $8961469859.95

- **Number of Shares Outstanding (Series):** 8961419805.8900

- **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 (%)   |
|:---|:---|:---|:---|:---|
| 2025-12-01 | $15785493347.54           | $15785493347.54            | 99.9300%                  | 99.9300%                   |
| 2025-12-02 | $15869897108.72           | $15869897108.72            | 99.9300%                  | 99.9300%                   |
| 2025-12-03 | $15972793953.05           | $15972793953.05            | 99.9200%                  | 99.9200%                   |
| 2025-12-04 | $15912434873.49           | $15912434873.49            | 99.9200%                  | 99.9200%                   |
| 2025-12-05 | $15947787940.90           | $15947787940.90            | 99.9200%                  | 99.9200%                   |
| 2025-12-08 | $16251135996.31           | $16251135996.31            | 99.9200%                  | 99.9200%                   |
| 2025-12-09 | $15940422956.12           | $15940422956.12            | 99.9100%                  | 99.9100%                   |
| 2025-12-10 | $16066596115.35           | $16066596115.35            | 99.9100%                  | 99.9100%                   |
| 2025-12-11 | $16152613654.07           | $16152613654.07            | 99.9100%                  | 99.9100%                   |
| 2025-12-12 | $16363936567.35           | $16363936567.35            | 99.9100%                  | 99.9100%                   |
| 2025-12-15 | $16483396234.52           | $16483396234.52            | 99.9100%                  | 99.9100%                   |
| 2025-12-16 | $16180810876.79           | $16180810876.79            | 99.9000%                  | 99.9000%                   |
| 2025-12-17 | $16376514044.03           | $16376514044.03            | 99.9000%                  | 99.9000%                   |
| 2025-12-18 | $16462970783.16           | $16462970783.16            | 99.9000%                  | 99.9000%                   |
| 2025-12-19 | $16707373204.94           | $16707373204.94            | 99.9000%                  | 99.9000%                   |
| 2025-12-22 | $17154210303.70           | $17154210303.70            | 99.9000%                  | 99.9000%                   |
| 2025-12-23 | $16742428709.67           | $16742428709.67            | 99.9000%                  | 99.9000%                   |
| 2025-12-24 | $17315016670.51           | $17315016670.51            | 99.9000%                  | 99.9000%                   |
| 2025-12-26 | $16998797986.67           | $16998797986.67            | 99.8900%                  | 99.8900%                   |
| 2025-12-29 | $16992419085.29           | $16992419085.29            | 99.8900%                  | 99.8900%                   |
| 2025-12-30 | $16827760714.17           | $16827760714.17            | 99.8900%                  | 99.8900%                   |
| 2025-12-31 | $17320268747.55           | $17320268747.55            | 99.8900%                  | 99.8900%                   |

### 7-Day Gross Yield
| Date       | 7-Day Gross Yield   |
|:---|:---|
| 2025-12-01 | 3.9600%             |
| 2025-12-02 | 3.9500%             |
| 2025-12-03 | 3.9500%             |
| 2025-12-04 | 3.9400%             |
| 2025-12-05 | 3.9200%             |
| 2025-12-08 | 3.9200%             |
| 2025-12-09 | 3.9200%             |
| 2025-12-10 | 3.9100%             |
| 2025-12-11 | 3.9100%             |
| 2025-12-12 | 3.8900%             |
| 2025-12-15 | 3.8900%             |
| 2025-12-16 | 3.8800%             |
| 2025-12-17 | 3.8700%             |
| 2025-12-18 | 3.8700%             |
| 2025-12-19 | 3.8500%             |
| 2025-12-22 | 3.8500%             |
| 2025-12-23 | 3.8400%             |
| 2025-12-24 | 3.8400%             |
| 2025-12-26 | 3.8200%             |
| 2025-12-29 | 3.8200%             |
| 2025-12-30 | 3.8200%             |
| 2025-12-31 | 3.8100%             |

### Daily Net Asset Value per Share (Series)
| Date       | Net Asset Value per Share   |
|:---|:---|
| 2025-12-01 | 1.0001                      |
|  |  |
| 2025-12-02 | 1.0002                      |
|  |  |
| 2025-12-03 | 1.0002                      |
|  |  |
| 2025-12-04 | 1.0002                      |
|  |  |
| 2025-12-05 | 1.0002                      |
|  |  |
| 2025-12-08 | 1.0002                      |
|  |  |
| 2025-12-09 | 1.0002                      |
|  |  |
| 2025-12-10 | 1.0003                      |
|  |  |
| 2025-12-11 | 1.0003                      |
|  |  |
| 2025-12-12 | 1.0003                      |
|  |  |
| 2025-12-15 | 1.0002                      |
|  |  |
| 2025-12-16 | 1.0003                      |
|  |  |
| 2025-12-17 | 1.0003                      |
|  |  |
| 2025-12-18 | 1.0003                      |
|  |  |
| 2025-12-19 | 1.0002                      |
|  |  |
| 2025-12-22 | 1.0002                      |
|  |  |
| 2025-12-23 | 1.0002                      |
|  |  |
| 2025-12-24 | 1.0002                      |
|  |  |
| 2025-12-26 | 1.0002                      |
|  |  |
| 2025-12-29 | 1.0002                      |
|  |  |
| 2025-12-30 | 1.0002                      |
|  |  |
| 2025-12-31 | 1.0002                      |
|  |  |

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

### Class: Class P

- **Minimum Initial Investment:** $1.00

- **Net Assets of Class:** $495388397.83

- **Number of Shares Outstanding:** 495383631.8800

- **Expense Reimbursement/Waiver:** 19373.00

**Daily Net Asset Value per Share (Class)**
| Date       | NAV per Share   |
|:---|:---|
| 2025-12-01 | 1.0001          |
|  |  |
| 2025-12-02 | 1.0002          |
|  |  |
| 2025-12-03 | 1.0002          |
|  |  |
| 2025-12-04 | 1.0002          |
|  |  |
| 2025-12-05 | 1.0002          |
|  |  |
| 2025-12-08 | 1.0002          |
|  |  |
| 2025-12-09 | 1.0002          |
|  |  |
| 2025-12-10 | 1.0003          |
|  |  |
| 2025-12-11 | 1.0003          |
|  |  |
| 2025-12-12 | 1.0003          |
|  |  |
| 2025-12-15 | 1.0002          |
|  |  |
| 2025-12-16 | 1.0003          |
|  |  |
| 2025-12-17 | 1.0003          |
|  |  |
| 2025-12-18 | 1.0003          |
|  |  |
| 2025-12-19 | 1.0003          |
|  |  |
| 2025-12-22 | 1.0002          |
|  |  |
| 2025-12-23 | 1.0002          |
|  |  |
| 2025-12-24 | 1.0002          |
|  |  |
| 2025-12-26 | 1.0002          |
|  |  |
| 2025-12-29 | 1.0002          |
|  |  |
| 2025-12-30 | 1.0002          |
|  |  |
| 2025-12-31 | 1.0002          |
|  |  |

**Daily Shareholder Flows**
| Date       | Gross Subscriptions ($)   | Gross Redemptions ($)   |
|:---|:---|:---|
| 2025-12-01 | $3074755.28               | $1692225.30             |
| 2025-12-02 | $8396539.54               | $6131511.86             |
| 2025-12-03 | $4571925.23               | $6766508.60             |
| 2025-12-04 | $6033800.73               | $8357551.90             |
| 2025-12-05 | $17515750.81              | $5878631.77             |
| 2025-12-08 | $3209767.04               | $3483861.54             |
| 2025-12-09 | $3901354.92               | $5947116.13             |
| 2025-12-10 | $3099314.08               | $8298424.18             |
| 2025-12-11 | $15157844.43              | $7692358.16             |
| 2025-12-12 | $8240236.56               | $4472337.27             |
| 2025-12-15 | $9759390.49               | $3887688.69             |
| 2025-12-16 | $13846856.60              | $5330835.99             |
| 2025-12-17 | $14337089.97              | $5912547.73             |
| 2025-12-18 | $2917756.10               | $8210481.97             |
| 2025-12-19 | $3782093.70               | $4651882.82             |
| 2025-12-22 | $14558078.77              | $7066861.11             |
| 2025-12-23 | $13294816.75              | $9627477.30             |
| 2025-12-24 | $10564672.31              | $5592983.55             |
| 2025-12-26 | $8222836.11               | $4871278.92             |
| 2025-12-29 | $8087221.39               | $3208024.55             |
| 2025-12-30 | $9860085.13               | $2690833.60             |
| 2025-12-31 | $11003867.73              | $2910593.83             |

**Total Gross Subscriptions (Month):** $193436053.67

**Total Gross Redemptions (Month):** $122682016.77

**7-Day Net Yield (Class)**
| Date       | 7-Day Net Yield   |
|:---|:---|
| 2025-12-01 | 3.8200%           |
| 2025-12-02 | 3.8100%           |
| 2025-12-03 | 3.8100%           |
| 2025-12-04 | 3.8000%           |
| 2025-12-05 | 3.7800%           |
| 2025-12-08 | 3.7800%           |
| 2025-12-09 | 3.7800%           |
| 2025-12-10 | 3.7700%           |
| 2025-12-11 | 3.7700%           |
| 2025-12-12 | 3.7500%           |
| 2025-12-15 | 3.7500%           |
| 2025-12-16 | 3.7400%           |
| 2025-12-17 | 3.7300%           |
| 2025-12-18 | 3.7300%           |
| 2025-12-19 | 3.7100%           |
| 2025-12-22 | 3.7100%           |
| 2025-12-23 | 3.7000%           |
| 2025-12-24 | 3.7000%           |
| 2025-12-26 | 3.6800%           |
| 2025-12-29 | 3.6800%           |
| 2025-12-30 | 3.6800%           |
| 2025-12-31 | 3.6700%           |

### Class: Class T

- **Minimum Initial Investment:** $5000000.00

- **Net Assets of Class:** $8466081462.12

- **Number of Shares Outstanding:** 8466036174.0100

- **Expense Reimbursement/Waiver:** 323955.00

**Daily Net Asset Value per Share (Class)**
| Date       | NAV per Share   |
|:---|:---|
| 2025-12-01 | 1.0001          |
|  |  |
| 2025-12-02 | 1.0002          |
|  |  |
| 2025-12-03 | 1.0002          |
|  |  |
| 2025-12-04 | 1.0002          |
|  |  |
| 2025-12-05 | 1.0002          |
|  |  |
| 2025-12-08 | 1.0002          |
|  |  |
| 2025-12-09 | 1.0002          |
|  |  |
| 2025-12-10 | 1.0003          |
|  |  |
| 2025-12-11 | 1.0003          |
|  |  |
| 2025-12-12 | 1.0003          |
|  |  |
| 2025-12-15 | 1.0002          |
|  |  |
| 2025-12-16 | 1.0003          |
|  |  |
| 2025-12-17 | 1.0003          |
|  |  |
| 2025-12-18 | 1.0003          |
|  |  |
| 2025-12-19 | 1.0002          |
|  |  |
| 2025-12-22 | 1.0002          |
|  |  |
| 2025-12-23 | 1.0002          |
|  |  |
| 2025-12-24 | 1.0002          |
|  |  |
| 2025-12-26 | 1.0002          |
|  |  |
| 2025-12-29 | 1.0002          |
|  |  |
| 2025-12-30 | 1.0002          |
|  |  |
| 2025-12-31 | 1.0002          |
|  |  |

**Daily Shareholder Flows**
| Date       | Gross Subscriptions ($)   | Gross Redemptions ($)   |
|:---|:---|:---|
| 2025-12-01 | $58013321.54              | $8960358.20             |
| 2025-12-02 | $12872326.23              | $30940554.65            |
| 2025-12-03 | $17320346.62              | $8551480.39             |
| 2025-12-04 | $103686793.36             | $15255224.86            |
| 2025-12-05 | $16818325.81              | $14739964.89            |
| 2025-12-08 | $10793842.43              | $11853848.75            |
| 2025-12-09 | $58084878.87              | $22491405.60            |
| 2025-12-10 | $4320183.26               | $30723821.37            |
| 2025-12-11 | $151613144.25             | $15682507.10            |
| 2025-12-12 | $347376280.85             | $19095105.65            |
| 2025-12-15 | $12807033.81              | $13812862.21            |
| 2025-12-16 | $21150123.15              | $9230266.14             |
| 2025-12-17 | $48079632.68              | $22500067.09            |
| 2025-12-18 | $388295043.26             | $175776755.01           |
| 2025-12-19 | $255032625.41             | $10226603.93            |
| 2025-12-22 | $283384710.34             | $70034648.78            |
| 2025-12-23 | $55529036.41              | $77496087.48            |
| 2025-12-24 | $59960291.89              | $18089114.48            |
| 2025-12-26 | $65822947.84              | $7002018.07             |
| 2025-12-29 | $7123583.36               | $99661477.74            |
| 2025-12-30 | $51659880.01              | $29140273.79            |
| 2025-12-31 | $14289953.39              | $3952744.78             |

**Total Gross Subscriptions (Month):** $2044034304.77

**Total Gross Redemptions (Month):** $715217190.96

**7-Day Net Yield (Class)**
| Date       | 7-Day Net Yield   |
|:---|:---|
| 2025-12-01 | 3.8200%           |
| 2025-12-02 | 3.8100%           |
| 2025-12-03 | 3.8100%           |
| 2025-12-04 | 3.8000%           |
| 2025-12-05 | 3.7800%           |
| 2025-12-08 | 3.7800%           |
| 2025-12-09 | 3.7800%           |
| 2025-12-10 | 3.7700%           |
| 2025-12-11 | 3.7700%           |
| 2025-12-12 | 3.7500%           |
| 2025-12-15 | 3.7500%           |
| 2025-12-16 | 3.7400%           |
| 2025-12-17 | 3.7300%           |
| 2025-12-18 | 3.7300%           |
| 2025-12-19 | 3.7100%           |
| 2025-12-22 | 3.7100%           |
| 2025-12-23 | 3.7000%           |
| 2025-12-24 | 3.7000%           |
| 2025-12-26 | 3.6800%           |
| 2025-12-29 | 3.6800%           |
| 2025-12-30 | 3.6800%           |
| 2025-12-31 | 3.6700%           |

## Part C: Schedule of Portfolio Securities

### Security 1: 100 [percent symbol] US Treasury Master Fund

- **C.1 - Title:** 100 [percent symbol] US Treasury Master Fund
- **C.6 - Investment Category:** Investment Company
- **Identifiers:** C.3 - CUSIP: 902656883, C.3 - LEI: 5299000M97HC3J8TJ387
- **C.18 - Value (incl. sponsor support):** $8989279027.90
- **C.18.a - Value (excl. sponsor support):** $8989279027.90
- **C.19 - Percentage of Net Assets:** 100.0000%
- **C.17 - Yield as of Reporting Date:** 0.0000%
- **C.11 - Maturity Date (WAM):** 2026-01-02
- **C.12 - Maturity Date (WAL):** 2026-01-02
- **C.13 - Final Legal Maturity Date:** 2026-01-02
- **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:** 2026-01-07

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

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

**Title of Signing Officer:** Vice President