Syensqo SA/NV — Proxy Solicitation & Information Statement 2026

Apr 3, 2026

To be valid, this vote by correspondence form should be duly completed and signed and transmitted to Syensqo SA by Wednesday 29 April 2026 at the latest, by e-mail (ag@syensqo.com) or by mail (Syensqo SA, Shareholders Service, 98 Rue de la Fusée, 1130 Brussels). In addition, shareholders must comply with the registration procedure described in the convening notice.

VOTE BY CORRESPONDENCE FORM FOR THE ORDINARY SHAREHOLDERS' MEETING OF SYENSQO SA 5 MAY 2026

I, the undersigned (name, first name and address or for legal entities: company name, registered office, name(s), first name(s) and capacity of the physical person(s) signing this vote by correspondence form on behalf of the legal entity shareholder)

owner of ___ Syensqo SA shares, on the record date, set on Tuesday 21 April 2026 at midnight,

exercise my voting right in the following way on the items of the agenda of the Shareholders' Meeting of Syensqo SA that will take place on Tuesday 5 May 2026 at SQUARE Brussels, Mont des Arts, 1000 Brussels, Belgium or any other subsequent shareholders' meetings with the same agenda.

This form must be completed with precise votes for each item on the agenda. In the absence of precise choice concerning one or more items on the agenda of the Shareholders' Meeting, this form will be considered null and void in its entirety. Shareholders who have cast their vote by validly returning this form may not vote by proxy at the Shareholders' Meeting for the number of votes already cast.

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AGENDA AND PROPOSED RESOLUTIONS

1. Reports and annual accounts
   1.1. Acknowledgment of the management report for the financial year 2025 - and the statutory auditor's report for the financial year 2025
   1.2. Acknowledgment of the consolidated annual accounts for the financial year 2025 – and the report of the statutory auditor on the consolidated annual accounts
   1.3. Approval of the statutory annual accounts for the financial year 2025 – Allocation of profit and determination of the dividend

Proposed resolution: it is proposed to approve the statutory annual accounts for the financial year 2025 and the allocation of profit for the financial year and to set the gross dividend per share at EUR 1.62 payable as from May 18, 2026.

FOR ☐ AGAINST ☐ ABSTAIN ☐

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2

1. Discharge to the Directors and to the Statutory Auditor

2.1. Discharge to the directors for the performance of their mandate during the financial year 2025

Proposed resolution: it is proposed to grant discharge to the directors for the performance of their mandate during the financial year 2025.

FOR ☐ AGAINST ☐ ABSTAIN ☐

2.2. Discharge to the statutory auditor for the performance of its mandate during the financial year 2025

Proposed resolution: it is proposed to grant discharge to the statutory auditor for the performance of its mandate during the financial year 2025.

FOR ☐ AGAINST ☐ ABSTAIN ☐

1. Remuneration Report

Proposed resolution: it is proposed to approve the 2025 remuneration report, included in the Corporate Governance Statement section of the management report for the financial year 2025.

FOR ☐ AGAINST ☐ ABSTAIN ☐

1. Appointment of directors

Proposed resolutions: upon recommendations by the Nomination Committee and upon proposals of the Board of Directors, it is proposed to

4.1. acknowledge the stepping down of Mrs. Nadine Leslie, effective June 30, 2025, Mr. Matti Lievonen, effective July 15, 2025, Mrs. Ilham Kadri, effective December 31, 2025, Mr. Roeland Baan, effective March 2, 2026, and Ms. Rosemary Thorne, effective March 31, 2026, from their mandate as directors of the Company.

4.2. confirm the co-optation of Mrs. Cynthia Arnold as non-executive director, and appoint her for a period of four (4) years, until the close of the Ordinary Shareholders' Meeting to be held in 2030. Her remuneration is set in accordance with the Remuneration Policy.

FOR ☐ AGAINST ☐ ABSTAIN ☐

4.3. acknowledge that (i) from the information made available to the Company, Mrs. Cynthia Arnold meets the independence criteria stipulated by Article 7:87 of the BCCA, by Principle 3.5 of the 2020 Belgian Code of Corporate Governance and by Article 5.2.4 of the Governance Charter of the Company and that (ii) the Board of Directors confirms that it has no indication to question the independence of the proposed candidate director, and consequently, appoint Mrs. Cynthia Arnold as independent director.

FOR ☐ AGAINST ☐ ABSTAIN ☐

4.4. confirm the co-optation of Mr. Augusto Di Donfrancesco, as non-executive director, and to appoint him for a period of four (4) years, until the close of the Ordinary Shareholders' Meeting to be held in 2030. His remuneration is set in accordance with the Remuneration Policy.

FOR ☐ AGAINST ☐ ABSTAIN ☐

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4.5. confirm the co-optation of Mr. Michael Radossich, as executive director, and appoint him for a period of four (4) years, until the close of the Ordinary Shareholders' Meeting to be held in 2030. His remuneration is set in accordance with the Remuneration Policy.

☐ FOR ☐ AGAINST ☐ ABSTAIN

4.6. confirm the co-optation of Mr. Miguel Mantas as non-executive director, and appoint him for a period of four (4) years, until the close of the Ordinary Shareholders' Meeting to be held in 2030. His remuneration is set in accordance with the Remuneration Policy.

☐ FOR ☐ AGAINST ☐ ABSTAIN

4.7. acknowledge that (i) from the information made available to the Company, Mr. Miguel Mantas meets the independence criteria stipulated by Article 7:87 of the BCCA, by Principle 3.5 of the 2020 Belgian Code of Corporate Governance and by Article 5.2.4 of the Governance Charter of the Company and that (ii) the Board of Directors confirms that it has no indication to question the independence of the proposed candidate director, and consequently, appoint Mr. Miguel Mantas as independent director.

☐ FOR ☐ AGAINST ☐ ABSTAIN

4.8. confirm the co-optation of Mrs Martine Snels as non-executive director, and appoint her for a period of four (4) years, until the close of the Ordinary Shareholders' Meeting to be held in 2030. Her remuneration is set in accordance with the Remuneration Policy.

☐ FOR ☐ AGAINST ☐ ABSTAIN

4.9. acknowledge that (i) from the information made available to the Company, Mrs Martine Snels meets the independence criteria stipulated by Article 7:87 of the BCCA, by Principle 3.5 of the 2020 Belgian Code of Corporate Governance and by Article 5.2.4 of the Governance Charter of the Company and that (ii) the Board of Directors confirms that it has no indication to question the independence of the proposed candidate director, and consequently, appoint Mrs Martine Snels as independent director.

☐ FOR ☐ AGAINST ☐ ABSTAIN

1. Appointment of the Statutory Auditor, Determination of Remuneration, and Appointment for the Assurance of Sustainability Reporting

Proposed resolutions: Upon recommendation of the Audit and Risk Committee issued pursuant to Article 16(2) of Regulation (EU) No. 537/2014 and on the basis of the summary of the selection procedure conducted in accordance with Article 16(3) thereof, it is proposed to:

5.1. appoint Ernst & Young Réviseurs d'Entreprises SRL (EY), with registered office at Kouterveldstraat 7B/1, 1831 Machelen, Belgium, represented by its permanent representative Ms. Marie Kaisin, as statutory auditor of the Company for a term of three (3) financial years, ending after the Ordinary Shareholders' Meeting to be held in 2029.

☐ FOR ☐ AGAINST ☐ ABSTAIN

5.2. set the remuneration of the statutory auditor for the statutory audit of the Company's annual and consolidated financial statements for each year of its mandate, at EUR 1.4 million per financial year (excluding VAT and out-of-pocket expenses).

☐ FOR ☐ AGAINST ☐ ABSTAIN

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5.3. appoint Ernst & Young Réviseurs d'Entreprises SRL (EY), represented by its permanent representative Ms. Marie Kaisin, to perform the limited assurance engagement on the Company's sustainability reporting, in accordance with Directive (EU) 2022/2464 and any applicable Belgian implementing legislation, for the same duration as its statutory audit mandate.

☐ FOR ☐ AGAINST ☐ ABSTAIN

5.4. set the remuneration of the statutory auditor for the specific assignment of the assurance of sustainability reporting at EUR 0.6 million per financial year (excluding VAT and out-of-pocket expenses).

☐ FOR ☐ AGAINST ☐ ABSTAIN

1. Delegation of powers

Proposed resolution: it is proposed to grant Ms. Valérie Demeur, Corporate Secretary, Ms. Olivia Szerer, Senior Legal Counsel, each acting individually with the right of substitution, with all powers to carry out the publication formalities necessary for the publication of the resolutions taken by the Ordinary Shareholders' Meeting, with power of substitution.

☐ FOR ☐ AGAINST ☐ ABSTAIN

1. Miscellaneous

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In case shareholders, in accordance with Article 7:130 of the Code of Companies and Associations, exercise their right to add items to the agenda and/or to submit resolution proposals with regard to existing agenda items or new items to be added to the agenda, the vote by correspondence forms submitted prior to the publication of the revised agenda shall remain valid for the agenda items that they cover. Syensqo SA will also make the revised agenda and a revised model of vote by correspondence form available on its website (https://www.syensqo.com/en/investors/shareholders-meetings) at the latest on Monday 20 April 2026, in order to allow shareholders who would wish to vote by correspondence on the new agenda items and/or new/alternative proposed resolutions.

In case new/alternative proposed resolutions are submitted with respect to agenda items existing after the notified vote by correspondence forms, shareholders will have the possibility to send a new vote by correspondence form to Syensqo SA, using the revised vote by correspondence form mentioned in the previous paragraph.

PROTECTION OF PERSONAL DATA

Syensqo SA processes the personal data of shareholders and proxy holders in connection with the Shareholders' Meeting in accordance with applicable data protection laws, including Regulation (EU) 2016/679 (GDPR). Such data is used to organize participation and voting, may be shared with service providers (in particular Lumi), and is processed to comply with Syensqo SA's legal obligations. Data is retained for up to 10 years after the meeting. Shareholders and proxy holders have rights regarding their personal data in accordance with applicable law. Further information is available in Syensqo SA's Data Protection and Privacy Policy (https://www.syensqo.com/en/information/data-protection-and-privacy-policy.html).

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Signed at

, on

2026.

Signature