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

COMPANHIA ABERTA

CNPJ 43.776.517/0001-80

NIRE 35300016831

MATERIAL FACT

Companhia de Saneamento Básico do Estado de São Paulo – Sabesp (“Company” or “Sabesp”), in compliance with Resolution 44 of the Brazilian Securities and Exchange Commission (CVM - Comissão de Valores Mobiliários), of August 23, 2021, and in continuity with the Relevant Facts disclosed on July 31, 2023 and September 18, 2023, hereby informs its shareholders and the market in general that, in a meeting held on April 17, 2024, State Privatization Board (CDPED - Conselho Diretor do Programa Estadual de Desestatização together with the Management Council of the State Program for Public-Private Partnerships (CGPPP - Conselho Gestor do Programa Estadual de Parcerias Público-Privadas) decided to approve the final model for the partial disposal of shares held directly and indirectly by the State, with authorization to proceed with the disposal through Public Offering Distribution of Shares on a stock exchange, according to the art.1, of Decree nº 67,759/2023, including:

(a) Schedule of the privatization process;

(b) Structure of the offer with the participation of strategic investors and criteria for judging the winner of the secondary public offering;

(c) Changes to the Company's Bylaws;

(d) Signing of an Investment Agreement, lock-up and other agreements with strategic investors;

(e) Guarantee of stability to employees in accordance with law no. 17,853/2023, for a period of 18 months, counting from the date of effective completion of the privatization process;

(f) Recommend the offer of common shares owned by the Government of the State of São Paulo to the Company's employees;

(g) Forwarding of following documents the representatives of the Deliberative Council of URAE – 1 Southeast for the 1st Council meeting:

The definition of the minimum price and the percentage of the State's share to be disposal, as well as the details of the Investment Agreement, Lock-up, and other conditions will be subject to deliberation at a future meeting of the Board.

The full meeting minutes are available at the following link:

The Company will keep the market informed regarding developments in the matter covered by this Material Fact.

São Paulo, April 18, 2024.

Catia Cristina Teixeira Pereira

Chief Financial Officer 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.