Annual and Extraordinary Shareholders Meeting - 04/28/2026- Call Notice

Publicly-held Company

CNPJ [National Register of Legal Entities] No. 43.776.517/0001-80 NIRE [State registration] 35.3000.1683-1

CALL NOTICE

The Shareholders of Companhia de Saneamento Básico do Estado de São Paulo - Sabesp ("Company"), pursuant to Article 9, paragraph 1, of its Bylaws, are hereby called to attend in the Annual and Extraordinary General Meeting ("AEGM" or "Meeting") to be held, on first call, at 11:00 a.m. (GMT-03:00) on April 28, 2026, exclusively digitally, through the "Ten Meetings" Platform, under the Brazilian Securities and Exchange Commission ("CVM") Resolution No. 81, of March 29, 2022 ("CVM Resolution 81/22"), in order to resolve on the following agenda:

ANNUAL GENERAL MEETING

1. To examine, discuss and vote on the management´s accounts and to examine, discuss and vote on the Company's financial statements for the fiscal year ended on December 31, 2025, together with the Management Report, the Independent Auditors' Report, the Fiscal Council's Opinion and the Audit Committee's Summary Annual Report;

2. To resolve on the allocation of the net income for the fiscal year ended on December 31, 2025;

3. To elect Mr. Eduardo Parente Menezes as a member of the Board of Directors, for the remainder of the current term of office, that is, until September 27, 2026;

4. To define the number of members that will comprise the Company's Fiscal Council for the next term of office;

5. To elect the members of the Company's Fiscal Council;

6. To set the limit on the annual global compensation of the management for the fiscal year to be ended on December 31, 2026; and

7. To set the compensation of the members of the Fiscal Council for the fiscal year to be ended on December 31, 2026.

EXTRAORDINARY GENERAL MEETING

1. The Restricted Share Plan - Estrela Bonus;

2. To amend the Company's Bylaws to:

   1. amend the caput of Article 3 to reflect (i) the capitalizations of profit reserves made in 2025 in the amount of BRL 6,210,000,000.00, and in 2026 in the amount of BRL 169,216,143.38 by resolution of the Board of Directors; and (ii) the existence of a special class preferred share (golden share) held by the State of São Paulo;

   2. amend the third paragraph of Article 3 to increase the authorized capital by adding 21,396,937 shares;

   3. include new first paragraphs in Articles 12, 18 and 26, to provide for the permanence of the members of the Board of Directors, the Board of Executive Officers and the Fiscal Council, respectively, in the exercise of their duties, until their respective successors take office, and renumber the subsequent paragraphs;

   4. amend the caput of Article 15 to adjust the minimum frequency of meetings of the Board of Directors from monthly to 8 meetings per year;

   5. amend paragraph ten of Article 15 to eliminate the requirement to prepare an excerpt of the minutes of the Board of Directors' meeting for filing with commercial boards and publication;

   6. amend item IV of Article 16 to limit the scope of authority of the Board of Directors to the approval of strategic and corporate policies;

   7. amend item XIX of Article 16 to change the name of the Eligibility and Compensation Committee to the People and Compensation Committee, and include the authority of the Board of Directors to elect and remove members of the statutory committees that may be created;

   8. amend item XXI of Article 16, the title of Chapter IX, Article 31, caput and sole paragraph, Article 32, caput and sole paragraph, and Article 43 to change the name of the Eligibility and Compensation Committee to People and Compensation Committee;

   9. delete item VIII of the first paragraph of Article 23 to organize the duties of the Chief Executive Officer (CEO) in accordance with the Company's practice;

   10. delete item IV of the second paragraph of Article 23 in order to eliminate repetition in the duties of the Chief Financial Officer and Investor Relations Officer and renumber the subsequent items;

   11. amend Article 37 to adapt the reporting lines of the compliance and risk management areas to the internal organizational structure;

   12. amend Article 38 to separate compliance and risk management assignments, with the creation of a new Article 39, renumber the subsequent articles and adjust cross-references;

   13. delete the second paragraph of Article 46 in view of the provision of the duties of the Committees in Internal Rules, with consequent renumbering of the first paragraph; and

   14. amend the sole paragraph of Article 58 to exclude the restriction that the pension plans sponsored by the Company be managed exclusively by a closed entity, under the defined contribution modality.

3. The stock split of common shares issued by the Company, whereby each 1 common share will be split into 5 common shares, without any change to the amount of the share capital, with the consequent amendment to the caput and paragraph three of Article 3 of the Bylaws; and

4. To restate the Company's Bylaws, to reflect the changes proposed in items "II" and "III" of the agenda of the Extraordinary General Meeting, if approved.

GUIDELINES FOR ATTENDING THE MEETING

In order to expand the participation of the Company's shareholder base, the Management considers it is more appropriate to hold the Meeting exclusively digitally.

Shareholders who wish to participate through Ten Meetings Platform ("Digital Platform") must pre-register on the Digital Platform at the following link https://assembleia.ten.com.br/919638884, by April 26, 2026, following the step by step indicated in the Meeting Participation Manual. Access to the Meeting will be restricted to shareholders and their representatives or proxies, who complete the registration process within the aforementioned deadline and whose registrations are duly validated by the Company.

We clarify that the shareholder may participate directly via the Digital Platform or through a duly appointed proxy.

Alternatively, shareholders may vote remotely through: (a) sending instructions for filling out the ballot to the respective custodian agents, in the case of shares are deposited with a central depositary;

(b) sending instructions for filling out the ballot to Itaú Corretora de Valores S.A., the Company's bookkeeping agent, in the case of shares are not deposited with a central depositary; (c) transmission of voting instructions through Ten Meetings Platform, (d) sending the remote voting ballot, available on the websites of CVM (www.cvm.gov.br), of the Company (https://ri.sabesp.com.br/), duly completed and signed, to email dri@sabesp.com.br; or (e) the electronic system made available by B3, in the Investor Area (available at https://www.investidor.b3.com.br/), in the "Services" section, by accessing on "Meetings in Progress".

In any of the above options, the shareholder must submit the following documentation:

• Individual - Individual Taxpayer's Register (CPF) and photo identification document of the shareholder or their legal representative*;

• Legal entity - (i) CPF and photo identification document of their legal representative*; (ii) amended and restated bylaws or articles of association**; and (iii) documents proving the granting of powers, including representation powers, if applicable;

• Investment Fund - (i) Fund regulations, (ii) bylaws or articles of the fund's administrator or

manager, and (iii) minutes of election of the legal representative(s) attending the meeting.

* Accepted identification documents: Identity Card (RG), Foreign National Register (RNE), Driver's

License (CNH) and professional registration card officially recognized in Brazil.

**For investment funds, the documents of the manager and/or administrator will be accepted, in compliance with the applicable voting policy.

On an exceptional basis, the Company waives the requirement for: (i) signature notarization on the documents submitted, (ii) the submission of certified copies; (iii) notarization and consularization or apostille of documents drawn up in a foreign language; (iv) sworn translation of: (a) documents in Portuguese, English or Spanish, and (b) documents in other languages, provided that they are accompanied by a simple translation into one of the aforementioned languages.

Equally on an exceptional basis, the Company shall not require the submission of the original remote voting ballot, as well as the signature notarization on the voting ballot signed in the Brazilian territory and the notarization and apostille or consularization of the voting ballot signed outside the country.

The shareholder shall be responsible for the accuracy and authenticity of all documents submitted.

Detailed information regarding documentation requirements for attending the Meeting either through the Digital Platform or through sending the remote voting ballot, as well as the rules for granting a power of attorney are included in the Meeting Participation Manual.

Each common share confer the right to one vote in the Meeting's resolutions, subject to the limits established in the Company's Bylaws. Pursuant to Article 6 of the Bylaws, any shareholder or "Group of Shareholders" (as defined therein) is prohibited from exercising voting rights in excess of 30% of the Company's voting share, regardless of their actual equity interest. Due to this limitation, the Company requests that shareholders belonging to any "Group of Shareholders" report this fact to the Company by 11:00 a.m. (GMT-03:00) on April 24, 2026, as identify the other shareholders that also are part of the same "Group of Shareholders".

Votes that exceed the limits set forth in Article 6 of the Company's Bylaws will not be counted.

The documents relevant to the Meeting are available to the shareholders at the Company's headquarters, on its Investor Relations website (https://ri.sabesp.com.br/) and on the CVM (https://www.gov.br/cvm) and B3 (http://www.b3.com.br/) websites.

Any questions or clarifications on the subjects of the agenda may be resolved or obtained by the following email: dri@sabesp.com.br.

São Paulo, March 27, 2026

Chairman of the Board of Directors