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: 31 December 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 December 2025

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

Voting Rights update

National Grid's registered capital as of 30 November 2025 consisted of 5,191,884,002 ordinary shares of which 230,339,116 were held as treasury shares; leaving a balance of 4,961,544,886 with voting rights.

The figure of 4,961,544,886 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

3 December 2025

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

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

This announcement is made in accordance with Article 19 of the Market Abuse Regulation ('MAR') and relates to the following PDMR acquiring shares following a partial vesting of an award made under the Company's Retention Award Plan ('RAP').

The vesting relates to a RAP award made to Talvis Love on 3 June 2024. The RAP award was conditional on continued employment with the Company and on the satisfaction of the performance conditions approved by the Remuneration Committee, which (after tax on the gross award) must be retained until the shareholding requirements are met. The RAP award remains subject to malus and clawback provisions.

In accordance with MAR, the relevant Financial Conduct Authority notifications are set out below.

Exhibit 99.3

09 December 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.

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: 31 December 2025