SEC Form 6-K filed by Companhia de saneamento Basico Do Estado De Sao Paulo - Sabesp

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

MATERIAL FACT

Companhia de Saneamento Básico do Estado de São Paulo – Sabesp ("Company") in compliance with the provisions of the Resolution of the Brazilian Securities and Exchange Commission ("CVM") No. 44, of August 23, 2021, as amended, and in continuity with the Material Facts disclosed on October 5, 2025, January 20, 2026 and January 21, 2026, informs its shareholders and the market in general that it has carried out, before the CVM, by virtue of the direct sale of control of Empresa Metropolitana de Águas e Energia S.A. – EMAE ("EMAE") to the Company, the filing of request for registration of a public tender offer to acquire up to all common shares issued by EMAE, except for those held, directly and indirectly, by the Company and for those eventually held in treasury, that is, up to 3,695,800 (three million, six hundred and nine and five thousand and eight hundred) common shares of EMAE on this date, which represent 10.0% of its total capital stock or 25.13% of its voting capital stock, pursuant to the provisions of article 254-A of Law No. 6,404, of December 15, 1976, as amended, as well as articles 45 and 46 of CVM Resolution No. 215 of October 10, 2024, as amended ("Tender Offer Shares" and "Tender Offer", respectively).

Subject to the terms and conditions to be set forth in the "Tender Offer Notice for the Acquisition of Common Shares by Sale of Control of EMAE – Empresa Metropolitana de Águas e Energia S.A.", the price per Tender Offer Share will be R$49.46 (forty-nine reais and forty-six cents) ("Price per Share"), corresponding to 80% (eighty percent) of the amount paid per share issued by EMAE, which was R$61.83^[1] (sixty-one reais and eighty-three cents), either by the 11,009,550 (eleven million, nine thousand, five hundred and fifty) common shares, or for the 29,950 (twenty nine thousand, nine hundred and fifty) preferred shares that were also acquired within the scope of the transaction, totaling R$682,643,113.65 (six hundred and eighty-two million, six hundred and forty-three thousand, one hundred and thirteen reais and sixty-five cents). The Price per Share will be updated by the SELIC Rate - variation of the weighted and adjusted average rate of financing operations for one day, backed by federal government securities, conducted in the Special Settlement and Custody System - since January 21, 2026, the date of closing of the transaction that resulted in the acquisition of the Company's controlling interest in EMAE, until the date of settlement of the Tender Offer.

The Company will keep its shareholders and the market informed of any relevant updates related to the subject matter of this Material Fact.

São Paulo, February 2, 2026

DANIEL SZLAK

Chief Financial and Investor Relations Officer

^[1] Updated value considering that in the Material Fact disclosed on January 21, 2026, the calculation of the value per share considered only the common shares issued by EMAE acquired by SABESP, and the total price of the transaction also includes the 29,950 preferred shares issued by EMAE acquired.