# EDGAR Filing Document

**Accession Number:** 0000917286
**File Stem:** 0000917286-25-000134
**Filing Date:** 2025-9
**Character Count:** 5422
**Document Hash:** 73f85ef73487704a40d3fb644ad78dff
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0000917286-25-000134.hdr.sgml**: 20250922

**ACCESSION NUMBER**: 0000917286-25-000134

**CONFORMED SUBMISSION TYPE**: 497

**PUBLIC DOCUMENT COUNT**: 27

**FILED AS OF DATE**: 20250922

**DATE AS OF CHANGE**: 20250922

**EFFECTIVENESS DATE**: 20250922

**FILER**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** FIDELITY HEREFORD STREET TRUST
- **CENTRAL INDEX KEY:** 0000917286

**ORGANIZATION NAME:**
- **EIN:** 000000000
- **STATE OF INCORPORATION:** DE
- **FISCAL YEAR END:** 0430

**FILING VALUES:**
- **FORM TYPE:** 497
- **SEC ACT:** 1933 Act
- **SEC FILE NUMBER:** 033-52577
- **FILM NUMBER:** 251329207

**BUSINESS ADDRESS:**
- **STREET 1:** 245 SUMMER STREET
- **CITY:** BOSTON
- **STATE:** MA
- **ZIP:** 02210
- **BUSINESS PHONE:** 617-563-7000

**MAIL ADDRESS:**
- **STREET 1:** 245 SUMMER STREET
- **CITY:** BOSTON
- **STATE:** MA
- **ZIP:** 02210

## Series and Classes Contracts Data

### Fidelity Treasury Digital Fund (Series ID: S000089156)

---

|  |  |  |
|:---|:---|:---|
| Class Name      | Ticker Symbol | Class ID   |
| Liquidity Class | FYHXX         | C000255665 |
| OnChain         | FYOXX         | C000261149 |

---

## Series and Classes Contracts Data

### Fidelity Treasury Digital Fund (Series ID: S000089156)

| Class ID   | Class Name      | Ticker Symbol   |
|:---|:---|:---|
| C000255665 | Liquidity Class | FYHXX           |
| C000261149 | OnChain         | FYOXX           |

?xml version='1.0' encoding='ASCII'? Prospectus - Investment Objective

**Supplement to the Fidelity® Treasury Digital Fund Liquidity June 28, 2025 Prospectus** 

The following information replaces similar information found in the "Fund Summary" section under the "Principal Investment Strategies" heading.

* Normally investing at least 99.5% of total assets in cash and U.S. Treasury securities. The fund intends to invest only in cash and U.S. Treasury securities with a remaining maturity of 93 days or less or issued with a maturity of 93 days or less. 

The following information replaces similar information found in the "Investment Details" section under the "Principal Investment Strategies" heading.

The Adviser normally invests at least 99.5% of the fund's total assets in cash and U.S. Treasury securities. The fund intends to invest only in cash and U.S. Treasury securities with a remaining maturity of 93 days or less or issued with a maturity of 93 days or less. The Adviser normally invests the fund's assets in securities whose interest is specifically exempt from state and local income taxes under federal law; such interest is not exempt from federal income tax.

The following information replaces similar information found in the "Investment Details" section under the "Principal Investment Risks" heading.

In response to market, economic, political, or other conditions, a fund may temporarily use a different investment strategy (including leaving a significant portion of the fund's assets uninvested or investing in repurchase agreements collateralized by U.S. Treasury obligations) for defensive purposes. Uninvested assets do not earn income for a fund, which may have a significant negative impact on the fund's yield and may prevent the fund from achieving its investment objective. The addition of repurchase agreements could cause a portion of the income from Fidelity® Treasury Digital Fund to be subject to state and local income taxes.

TDL-PSTK-0925-100 1.9921544.100 September 22, 2025

**Supplement to the Fidelity® Treasury Digital Fund OnChain July 25, 2025 Prospectus** 

The following information replaces similar information found in the "Fund Summary" section under the "Principal Investment Strategies" heading.

* Normally investing at least 99.5% of total assets in cash and U.S. Treasury securities. The fund intends to invest only in cash and U.S. Treasury securities with a remaining maturity of 93 days or less or issued with a maturity of 93 days or less. 

The following information replaces similar information found in the "Investment Details" section under the "Principal Investment Strategies" heading.

The Adviser normally invests at least 99.5% of the fund's total assets in cash and U.S. Treasury securities. The fund intends to invest only in cash and U.S. Treasury securities with a remaining maturity of 93 days or less or issued with a maturity of 93 days or less. The Adviser normally invests the fund's assets in securities whose interest is specifically exempt from state and local income taxes under federal law; such interest is not exempt from federal income tax.

The following information replaces similar information found in the "Investment Details" section under the "Principal Investment Risks" heading.

In response to market, economic, political, or other conditions, a fund may temporarily use a different investment strategy (including leaving a significant portion of the fund's assets uninvested or investing in repurchase agreements collateralized by U.S. Treasury obligations) for defensive purposes. Uninvested assets do not earn income for a fund, which may have a significant negative impact on the fund's yield and may prevent the fund from achieving its investment objective. The addition of repurchase agreements could cause a portion of the income from Fidelity® Treasury Digital Fund to be subject to state and local income taxes.

TDLO-PSTK-0925-100 1.9921546.100 September 22, 2025