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 nº 43.776.517/0001-80 NIRE nº 35.3000.1683-1 FATO RELEVANTE Companhia de Saneamento Básico do Estado de São Paulo – Sabesp (“Company” or “Sabesp”), in compliance with the provisions of the Brazilian Securities Commission (“CVM”) Resolution No. 44, dated August 23, 2021, as amended, informs its shareholders and the market in general that ARSESP Resolution No. 1,748/2025 (“Resolution”) has been published in the State Official Gazette. According to the Resolution, the Company is authorized to apply an average adjustment of 6.5% to the current rates charged to users, effective as of January 1, 2026. Based on a preliminary review by the Company, this amount represents an increase of 10.6% in the equilibrium rate. Sabesp will work throughout the day to provide further clarification on the main items of the rate adjustment and will keep the market informed of any developments. Along with the Resolution, a Technical Note and an Excel Model were also published, which can be accessed directly on ARSESP’s website. The Company will keep its shareholders and the market informed of any developments in this matter. São Paulo, December 2, 2025. DANIEL SZLAK CFO and IRO 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.