NGG 6-K

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington D.C. 20549

FORM 6-K

REPORT OF FOREIGN PRIVATE ISSUER PURSUANT TO RULE 13a-16 OR 15d-16 UNDER THE SECURITIES EXCHANGE ACT OF 1934

Date: 29 August 2025

Commission File Number: 001-14958

NATIONAL GRID plc

(Translation of registrant’s name into English)

England and Wales

(Jurisdiction of Incorporation)

1-3 Strand, London, WC2N 5EH, United Kingdom

(Address of principal executive office)

Indicate by check mark whether the registrant files or will file annual reports under cover of Form 20-F or Form 40-F.

☒  Form 20-F      ☐  Form 40-F

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(1):  ☐

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(7):  ☐

Indicate by check mark whether the registrant by furnishing the information contained in this Form is also thereby furnishing the information to the Commission pursuant to Rule 12g3- 2(b) under the Securities Exchange Act of 1934.  ☐  Yes    ☒  No

If “Yes” is marked, indicate below the file number assigned to the registrant in connection with Rule 12g3-2(b): n/a

EXHIBIT INDEX

Exhibit 99.1

1 August 2025

National Grid plc ('National Grid' or 'Company')

Voting Rights update

National Grid's registered capital as of 31 July 2025 consisted of 5,191,884,002 ordinary shares, of which, 230,653,898 were held as treasury shares; leaving a balance of 4,961,230,104 with voting rights.

The figure of 4,961,230,104 may be used by shareholders as the denominator for the calculations by which they will determine if they are required to notify their interest in, or a change to their interest in, National Grid under the FCA's Disclosure Guidance and Transparency Rules.

Julian Baddeley

Group Company Secretary

Exhibit 99.2

8 August 2025

National Grid plc ('National Grid' or 'Company')

Notification of Transactions of Persons Discharging Managerial Responsibilities ('PDMRs')

This announcement is made in accordance with Article 19 of the Market Abuse Regulation ('MAR'). In accordance with MAR, the relevant Financial Conduct Authority ('FCA') notifications are set out below.

Exhibit 99.3

19th August 2025

National Grid plc / National Grid Electricity Transmission plc

Publication of a Prospectus

The following prospectus has been approved by the Financial Conduct Authority and is available for viewing:

The Prospectus dated 19 August 2025 (the "Prospectus") for the National Grid plc and National Grid Electricity Transmission plc Euro 20,000,000,000 Euro Medium Term Note Programme.

To view the full document, please paste the following URL into the address bar of your browser:

http://www.rns-pdf.londonstockexchange.com/rns/9476V_1-2025-8-19.pdf

A copy of the Prospectus has been submitted to the National Storage Mechanism and will shortly be available to the public for inspection at https://data.fca.org.uk/#/nsm/nationalstoragemechanism.

For further information, please contact:

DISCLAIMER - INTENDED ADDRESSEES

Please note that the information contained in the Prospectus may be addressed to and/or targeted at persons who are residents of particular countries (specified in the Prospectus) only and is not intended for use and should not be relied upon by any person outside these countries and/or to whom the offer contained in the Prospectus is not addressed. Prior to relying on the information contained in the Prospectus you must ascertain from the Prospectus whether or not you are part of the intended addressees of the information contained therein.

Your right to access this service is conditional upon complying with the above requirement.

SIGNATURE

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

Date: 29 August 2025