SABESP reports validated 2023 R$78.5B and 2024 R$88.0B RAB

Rhea-AI Filing Summary

Companhia de Saneamento Básico do Estado de São Paulo – SABESP announced that the São Paulo State Public Services Regulatory Agency (ARSESP) has validated its Regulatory Asset Base (RAB) for 2023 and 2024. The company reports a validated 2023 RAB of R$ 78.5 billion at June 2024 values and a validated 2024 RAB of R$ 88.0 billion at December 2024 values. These figures reflect adjustments such as reclassifications, construction margin, interest differences between IFRS and regulatory criteria, one-off asset revaluations, write-offs, inflation effects and depreciation, as summarized in the table. Management notes that forward-looking statements about future performance and strategies are subject to risks and uncertainties that could cause actual results to differ materially from current expectations.

Insights

Regulated utilities & valuation analyst

ARSESP validated SABESP’s 2023–2024 RAB, with 2024 set at R$ 88.0B.

The key disclosure is ARSESP’s validation of SABESP’s Regulatory Asset Base (RAB) for 2023 and 2024. The validated 2023 RAB is R$ 78.5 billion at June 2024 values, and the validated 2024 RAB is R$ 88.0 billion at December 2024 values, after a series of adjustments, including reclassifications, unqualified amounts, construction margin, interest differences, asset revaluations, write-offs, inflation and depreciation.

For a regulated water and sanitation company like SABESP, the RAB is an important reference for tariff setting and allowed returns, but this disclosure focuses on the mechanics and results of the validation rather than any explicit tariff impact. The filing does not quantify how these validated amounts translate into revenues or returns, so the financial implications depend on future regulatory applications.

The company also reiterates that any expectations about future performance, strategies, capital expenditures or dividend payments are forward-looking statements subject to economic, market, industry and operational risks. Subsequent regulatory and corporate communications will determine how the validated RAB is reflected in future financial outcomes.

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 November, 2025

(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 ESTADO DE SÃO PAULO – SABESP Publicly-held company CNPJ No. 43.776.517/0001-80 NIRE No. 35.3000.1683-1 MATERIAL FACT Companhia de Saneamento Básico do Estado de São Paulo – Sabesp (the “Company”), in compliance with the provisions of Resolution No. 44, of August 23, 2021, as amended, issued by the Brazilian Securities and Exchange Commission (“CVM”), hereby informs its shareholders and the market in general the validation by the São Paulo State Public Services Regulatory Agency (“ARSESP”) of the Regulatory Asset Base (“RAB”) for 2023 and 2024, as per the table below. In R$ billion (a) RAB(1) 23 @ Jun/24 Values 78,7 (b) Reclass from (a) to Passthrough 2026 (0,4) (c) Unqualified Amounts from (a) (0,4) (d) Construction Margin from (a) (0,5) (e) Interest (IFRS x Regulation) from (a) (1,0) (f) One-off Asset revaluation from (a) 2,1 (g) Validated 23 RAB @ Jun/24 Values 78,5 (g) = Σ (a) to (f) (h) Gross Additions to (g) 9,2 (i) Reclass from (h) to Passthrough 2026 (0,1) (j) Unqualified Amounts from (h) (0,6) (k) Construction Margin from (h) (0,2) (l) Interest (IFRS x Regulation) from (h) (0,3) (m) RAB write-offs from (g) (0,2) (n) One-off Asset revaluation from (g) 0,2 (o) Inflation over (g) and (h) from Jun/24 to Dec/24 2,0 (p) FY24 Depreciation over Gross RAB @ 2.35% per year (3,3) (q) FMSAI Prepayment 2,7 (r) Validated 24 RAB @ Dec/24 Values 88,0 (r) = Σ (g) to (q) (1) Appendix VIII Concession Contract São Paulo, November 24, 2025. DANIEL SZLAK CFO and IRO

 

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: November 25, 2025

Companhia de Saneamento Básico do Estado de São Paulo - SABESP
By:	/s/  Daniel Szlak
	Name: Daniel Szlak 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.

FAQ

What did SABESP (SBS) announce in this Form 6-K?

SABESP reported that the São Paulo State Public Services Regulatory Agency (ARSESP) validated its Regulatory Asset Base (RAB) for 2023 and 2024, detailing the calculation through a series of adjustments and movements in a summary table.

What is SABESP’s validated RAB amount for 2023?

SABESP reports a validated 2023 RAB of R$ 78.5 billion, presented at June 2024 values after adjustments including reclassifications, construction margin, interest differences, one-off asset revaluations and write-offs.

What is SABESP’s validated RAB amount for 2024?

The company reports a validated 2024 RAB of R$ 88.0 billion at December 2024 values, after incorporating gross additions, reclassifications, construction margin, interest differences, RAB write-offs, one-off revaluations, inflation and full-year depreciation.

Why is the Regulatory Asset Base (RAB) important for SABESP?

The RAB is a core regulatory measure of SABESP’s asset base used by the regulator as a reference when determining allowed returns and tariff frameworks. The filing presents the validated RAB amounts but does not detail specific tariff or revenue impacts.

Did SABESP provide details on how the RAB moved from 2023 to 2024?

Yes. SABESP includes a table showing items such as gross additions of R$ 9.2 billion, reclassifications to passthrough items, unqualified amounts, construction margin, interest differences, RAB write-offs, one-off revaluations, inflation of R$ 2.0 billion and depreciation of R$ 3.3 billion that reconcile to the validated 2024 RAB.

Does this SABESP filing include forward-looking statements?

Yes. SABESP states that certain comments about dividends, strategies, capital expenditure plans, future operations and factors affecting financial condition are forward-looking statements, which depend on assumptions about economic, market, industry and operating conditions and may differ materially from actual results.

Who signed the SABESP Form 6-K related to the RAB validation?

The report was signed on behalf of SABESP by Daniel Szlak, who is identified as the company’s Chief Financial Officer and Investor Relations Officer, in São Paulo, Brazil.