Reckitt Benckiser Group PLC — Capital/Financing Update 2026

May 19, 2026

SUPPLEMENTARY PROSPECTUS DATED 15 MAY 2026 TO THE BASE PROSPECTUS DATED 29 AUGUST 2025

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Reckitt Benckiser Treasury Services plc

( incorporated as a public limited company in England and Wales with registered number 05960843 )

Guaranteed by

Reckitt Benckiser Group plc

( incorporated as a public limited company in England and Wales with registered number 06270876 )

£10,000,000,000 Euro Medium Term Note Programme

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This Supplementary Prospectus (the “ Supplementary Prospectus ”, which definition shall also include all information incorporated by reference herein) to the base prospectus dated 29 August 2025 (the “ Base Prospectus ”, which definition includes the Base Prospectus as supplemented, amended or updated from time to time and includes all information incorporated by reference therein), constitutes a supplementary prospectus for the purposes of Section 87G of the Financial Services and Markets Act 2000 and is prepared in accordance with the £10,000,000,000 Euro Medium Term Note Programme (the “ Programme ”) established by Reckitt Benckiser Treasury Services plc (“ Reckitt ” or the “ Issuer ”) and guaranteed by Reckitt Benckiser Group plc (the “ Guarantor ”). Terms defined in the Base Prospectus have the same meaning when used in this Supplementary Prospectus.

This Supplementary Prospectus is supplemental to, and should be read in conjunction with, the Base Prospectus issued by the Issuer and all documents which are incorporated herein or therein by reference.

This Supplementary Prospectus has been approved by the United Kingdom Financial Conduct Authority (the “ FCA ”), which is the competent authority for the purposes of Regulation (EU) 2017/1129 as it forms part of the domestic law of the United Kingdom by virtue of the European Union (Withdrawal) Act 2018 (as amended) (the “ UK Prospectus Regulation ”), as a supplementary prospectus to the Base Prospectus. The Base Prospectus constitutes a base prospectus prepared in compliance with the UK Prospectus Regulation for the purpose of giving information with regard to the issue of Notes under the Programme.

The Issuer accepts responsibility for the information contained in this Supplementary Prospectus. To the best of the knowledge of the Issuer (having taken all reasonable care to ensure that such is the case), the information contained in this Supplementary Prospectus is in accordance with the facts and this Supplementary Prospectus does not omit anything likely to affect its import.

The purpose of this Supplementary Prospectus is to:

• (i) incorporate by reference into the Base Prospectus the Annual Report and Accounts of the Guarantor for the year ended 31 December 2025 (including, without limitation, the audited consolidated financial statements, auditor’s report thereon and notes thereto) (as defined below);

• (ii) incorporate by reference into the Base Prospectus the Q1 Results 2026 (as defined below) of the Guarantor;

• (iii) update the section of the Base Prospectus titled “Description of the Issuer and Guarantor”, following certain board appointments, updates and resignations; and

• (iv) update the “Significant/Material Change” statement in the Base Prospectus in respect of the Guarantor.

1. DOCUMENTS INCORPORATED BY REFERENCE

Reckitt Benckiser Group plc: Annual Report and Accounts

On 25 March 2026, the Guarantor published its Annual Report and Accounts for the year ended 31 December 2025 (the “ Annual Report and Accounts ”). The Annual Report and Accounts can be found at:

• https://eu

assets.contentstack.com/v3/assets/blt93c8bc7a598af9f0/blt3a6f2cd6ab14bf47/69c2b35aa17ac75c0a 18f6f2/Reckitt_Annual_Report_and_Accounts_2025_(2).pdf.

The Annual Report and Accounts include, on pages 117-197, the audited consolidated financial statements (including the auditor’s report thereon and notes thereto) for the year ended 31 December 2025. By virtue of this Supplementary Prospectus, the Annual Report and Accounts are hereby incorporated in, and form part of, this Supplementary Prospectus (and are thereby incorporated in, and form part of, the Base Prospectus).

Reckitt Benckiser Group plc: Alternative Performance Measures (“APMs”)

Certain APMs are included or referred to in the Annual Report and Accounts. APMs are non-GAAP measures used by the Group within its financial publications to supplement disclosures prepared in accordance with other regulations such as IFRS and the Solvency UK Directive. The Issuer considers that these measures provide useful information to enhance the understanding of financial performance. The APMs should be viewed as complementary to, rather than a substitute for, the figures determined according to other regulatory measures. An explanation of each such metric's components and

calculation method can be found at pages 203-209 (incorporated by reference herein) of the Annual Report and Accounts.

Reckitt Benckiser Group plc: Q1 Results 2026

On 22 April 2026, the Guarantor published its unaudited interim results for the three months to 31 March 2026 (the “ Q1 Results 2026 ”). The Q1 Results 2026 can be found at:

• https://eu

assets.contentstack.com/v3/assets/blt93c8bc7a598af9f0/bltc4e963d36c94c10d/69e8533c1ff49a3539 69bb41/Reckitt_Q1_2026.pdf.

By virtue of this Supplementary Prospectus, the Q1 Results 2026 are hereby incorporated in, and form part of, this Supplementary Prospectus (and are thereby incorporated in, and form part of, the Base Prospectus).

2. BOARD APPOINTMENTS AND RESIGNATIONS

With effect from the date of this Supplementary Prospectus:

The sub-section of the Base Prospectus titled “Directors” under “Reckitt Benckiser Treasury Services plc” in the “Description of the Issuer and Guarantor” on page 118 of the Base Prospectus is amended to:

• (a) include the appointment of James Hodges (business address: Turner House, 103-105 Bath Road, Slough, Berkshire, SL1 3UH) as Company Secretary. There is no potential conflict of interest between any of his duties to Reckitt Benckiser Treasury Services plc and his private interests and/or other duties; and

• (b) remove Sally Kenward as Company Secretary.

The sub-section of the Base Prospectus titled “Directors” under “Reckitt Benckiser Group plc” in the “Description of the Issuer and Guarantor” on page 119-120 of the Base Prospectus is amended to:

• (a) include the appointment of Deepak Nath (business address: Turner House, 103-105 Bath Road, Slough, Berkshire, SL1 3UH) as a Non-Executive Director. There is no potential conflict of interest between any of his duties to Reckitt Benckiser Group plc and his private interests and/or other duties;

• (b) include the appointment of Harry Kirsch (business address: Turner House, 103-105 Bath Road, Slough, Berkshire, SL1 3UH) as a Non-Executive Director. There is no potential conflict of interest between any of his duties to Reckitt Benckiser Group plc and his private interests and/or other duties;

• (c) remove Mahesh Madhavan as a Non-Executive Director; and

• (d) remove Margherita Della Valle as a Non-Executive Director.

3. SIGNIFICANT/MATERIAL CHANGE

The Significant/Material Change statement of the Guarantor at page 130 of the Base Prospectus is updated as set out below:

“Since 31 December 2025, there has been no material adverse change in the prospects of the Guarantor, and there has been no significant change in the Guarantor's financial position or financial performance.”

4. GENERAL

Copies of all documents or information incorporated by reference in this Supplementary Prospectus and the Base Prospectus can be obtained from the Issuer as described in the Base Prospectus or are otherwise available for viewing free of charge on the website of the Regulatory News Service operated by the London Stock Exchange at www.londonstockexchange.com/exchange/news/marketnews/marketnews-homes.html.

To the extent there is any inconsistency between (a) any statement in this Supplementary Prospectus or any statement incorporated by reference into the Base Prospectus by this Supplementary Prospectus and (b) any other statement in or incorporated by reference in the Base Prospectus prior to the date of this Supplementary Prospectus, the statements in (a) above will prevail.

If documents which are incorporated by reference themselves incorporate any information or other documents therein, either expressly or implicitly, such information or other documents will not form part of this Supplementary Prospectus for the purposes of the UK Prospectus Regulation except where such information or other documents are specifically incorporated by reference to this Supplementary Prospectus or where this Supplementary Prospectus is specifically defined as including such information.

Save as disclosed in this Supplementary Prospectus, any other supplement previously issued by the Issuer and the Base Prospectus, the Issuer is not aware of any other significant new factor, material mistake or inaccuracy relating to information included in the Base Prospectus which is capable of affecting an informed assessment by investors of Notes issued under the Programme since the publication of the Base Prospectus.

No person is authorised to give any information or to make any representation not contained in the Base Prospectus or this Supplementary Prospectus, and any information or representation not so contained must not be relied upon as having been authorised by or on behalf of the Issuer or the Dealers. The delivery of the Base Prospectus and/or this Supplementary Prospectus at any time does not imply that there has been no change in the affairs of the Issuer since the date hereof, or that the information contained in either of them is correct as at any time subsequent to each of their respective dates.

THIS SUPPLEMENTARY PROSPECTUS IS DATED 15 MAY 2026.