SBS 6-K 2026 - Equibles

SECURITIES AND EXCHANGE COMMISSION

Washington, DC 20549

FORM 6-K

REPORT OF FOREIGN ISSUER PURSUANT TO RULE 13a-16 OR 15d-16 OF THE

SECURITIES EXCHANGE ACT OF 1934

For April, 2026 (Commission File No. 1-31317)

Companhia de Saneamento Básico do Estado de São Paulo - SABESP

(Exact name of registrant as specified in its charter)

Basic Sanitation Company of the State of Sao Paulo - SABESP

(Translation of Registrant's name into English)

Rua Costa Carvalho, 300 São Paulo, S.P., 05429-900 Federative Republic of Brazil

(Address of Registrant's principal executive offices)

Indicate by check mark whether the registrant files or will file annual reports under cover Form 20-F or Form 40-F.

Form 20-F ___X___ Form 40-F ______

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(1)__.

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(7)__.

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___

If "Yes" is marked, indicated below the file number assigned to the registrant in connection with Rule 12g3-2(b):

COMPANHIA DE SANEAMENTO BÁSICO DO ESTADODE 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 Brazilian Securities Commission (“CVM”) Resolution No. 44, of August 23, 2021, as amended, and further to the Material Fact disclosed on October 5, 2025, which informed the market about the transaction involving Empresa Metropolitana de Águas e Energia S.A. – EMAE (“Transaction”), informs its shareholders and the market in general that:

(i)	the Administrative Council for<br>Economic Defense – CADE unanimously denied the appeal filed by Phoenix Água e Energia S.A., upholding the decision that approved<br>the Transaction without restrictions. The certificate of final judgment for the Operation was published on this date; and
(ii)	the National Electric Energy<br>Agency – ANEEL, at its 1st Regular Public Meeting of 2026, held on January 20, 2026, unanimously approved the request for prior<br>consent to the Transaction, pursuant to the applicable regulations.
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The effective completion of the transfer of corporate control to the Company depends on additional formalities set forth in the respective purchase and sale agreements executed with Vórtx Distribuidora de Títulos e Valores Mobiliários Ltda. and Axia Energia, which are in the implementation phase.

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, January 20, 2026

DANIEL SZLAK

Chief Financial and Investor Relations Officer

SIGNATURE

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.

Date: April 4, 2026

Companhia de Saneamento Básico do Estado de São Paulo - SABESP
By:	/s/ Daniel Szlak <br><br> <br>* * *
	Name: Daniel Szlak<br><br><br> <br>Title: Chief Financial Officer and Investor Relations Officer

FORWARD-LOOKING STATEMENTS

This press release may contain forward-looking statements. These statements are statements that are not historical facts, and are based on management's current view and estimates of future economic circumstances, industry conditions, company performance and financial results. The words "anticipates", "believes", "estimates", "expects", "plans" and similar expressions, as they relate to the company, are intended to identify forward-looking statements. Statements regarding the declaration or payment of dividends, the implementation of principal operating and financing strategies and capital expenditure plans, the direction of future operations and the factors or trends affecting financial condition, liquidity or results of operations are examples of forward-looking statements. Such statements reflect the current views of management and are subject to a number of risks and uncertainties. There is no guarantee that the expected events, trends or results will actually occur. The statements are based on many assumptions and factors, including general economic and market conditions, industry conditions, and operating factors. Any changes in such assumptions or factors could cause actual results to differ materially from current expectations.