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 ___X___

COMPANHIA DE SANEAMENTO BÁSICO DO ESTADO DE SÃO PAULO – SABESP

PUBLICLY HELD COMPANY

CNPJ 43.776.517/0001-80

NIRE nº 35.3000.1683-1

NOTICE TO THE MARKET

Companhia de Saneamento Básico do Estado de São Paulo – Sabesp (“Company” or “Sabesp”), in compliance with the provisions of the Brazilian Securities and Exchange Commission (“CVM”) Resolution No. 44, dated August 23, 2021, and Article 28 of CVM Resolution No. 23, dated February 2021, informs its shareholders and the market in general that its Board of Directors, in a meeting held on May 12, 2025, approved the hiring of Ernst & Young Auditores Independentes S/S Ltda. ("EY") as the independent auditing firm responsible for auditing the annual financial statements and reviewing the Company's quarterly financial information, replacing BDO RCS Auditores Independentes – Sociedade Simples Limitada (“BDO”), which had been responsible for providing these services until then. This change aims to synchronize the work and avoid duplication of efforts in obtaining and providing documents, as EY already provides auditing services to the Company's reference investor. BDO will continue to support the Company in other activities.

The services provided by EY will commence with the review of the financial information for the quarter ending June 30, 2025. The approval of EY's hiring considered the favorable opinion of the Audit Committee, issued in a meeting held on May 7, 2025, and had the consent of BDO.

São Paulo, May 21, 2025

DANIEL SZLAK

Chief Financial and Investor Relations Officer 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, in the city São Paulo, Brazil.