Sabesp (NYSE: SBS) outlines 10.6% equilibrium rate and 6.5% tariff hike

Rhea-AI Filing Summary

Sabesp is detailing a regulator-approved adjustment to its water and sewage tariffs. The company reports a 10.6% increase in the equilibrium rate, which is the technical rate level used in the regulatory framework. This change reflects factors such as recognition of the regulatory asset base, operating expenses, non-manageable costs, compensatory adjustments from the prior regulatory cycle, and other financial items.

After incorporating market effects, inflation measured by IPCA between July 2024 and October 2025, and tax items related to PIS/COFINS, Sabesp calculates that the average tariff applied to users will rise by 6.5%. The company links part of the improvement in operating items to a higher number of connections and volumes, driven by anticipated universalization of services, while also noting the end of rate coverage for the Alto Tietê PPP as a negative factor. These changes define the new price levels customers will pay going forward.

Positive

• Regulator-approved rate increase: Sabesp reports a 10.6% rise in the equilibrium rate and an average 6.5% increase in user tariffs, supporting higher regulated price levels.

Negative

• None.

Insights

Equity analyst – Latin American utilities

Regulator-approved tariff changes lift Sabesp’s allowed rates and user prices.

Sabesp describes a 10.6% increase in its equilibrium rate under ARSESP Resolution No. 1,748/2025. This stems from items such as lag in regulatory asset base recognition, operating expenses, non-manageable expenses, compensatory adjustments for the 4th regulatory cycle from 2021–2024, and other financial components. Together with market effects and inflation, these elements define the company’s updated regulated revenue framework.

The company also highlights specific drivers: higher connections and volumes from anticipated universalization support operating improvements, while the end of rate coverage for the Alto Tietê PPP reduces non-manageable expense recovery by about R$130 million. These offsetting effects are folded into the equilibrium rate calculation alongside regulatory asset remuneration and social-tariff and performance-bonus mechanisms.

After factoring in inflation (IPCA from Jul/24 to Oct/25) and tax changes captured in “delta PIS COFINS,” Sabesp estimates an average tariff adjustment of 6.5% for users. This means customer bills, on average, will be 6.5% higher than before the adjustment, within the parameters set by the regulator.

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 December, 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 (“Company” or “Sabesp”), in compliance with the provisions of the Brazilian Securities Commission (“CVM”) Resolution No. 44, dated August 23, 2021, as amended, and as a complement to the Material Fact disclosed on December 2, 2025, informs its shareholders and the market in general of further details regarding the rate adjustment authorized by ARSESP Resolution No. 1,748/2025 (“Resolution”).

The increase in the equilibrium rate of 10.6% is explained as follows:

(a)	Lag in RAB recognition	3.54%
(b)	Opex	1.42%
(c)	Non-Manageable Expenses	-0.41%
(d)	Regulatory Asset Base	0.63%
(e)	Compensatory Adjustment 4th cycle	-5.37%
(f)	Other Financial Items	0.68%
(g)	Equilibrium Rate Adjustment (real terms)	0.50%	= ∑ (a) to (f)
(h)	Market Effects	3.41%
(i)	Inflation	6.11%
(j)	Total before taxes	10.26%	=(1+g+h)*(1+i)-1
(k)	Delta PIS COFINS	0.36%
(l)	Total with taxes	10.65%	=(1+k)*(1+j)-1

(a) Correction since Aug/24 eliminating the timing mismatch. Values prior to Aug/24 were not considered as they precede the effective date of the URAE-1 contract.

(b) Improvement due to increased number of connections and volume, driven by the anticipation of universalization.

(c) Main impact related to the end of rate coverage for the Alto Tietê PPP (-R$130 million).

(d) Remuneration of the regulatory asset base.

(e) Compensatory adjustment for the 4^th cycle (2021–2024), judicial demands, and reforms and cancellations from the 4^th cycle.

(f) Removal of financial components from the initial rate, more than offset by performance bonuses, social rate (ARSESP Resolution 1,544/2024), FMSAI rates, among others.

(h) Effects of volume and consumption mix by rate class.

(i) IPCA from Jul/24 to Oct/25.

(k) Update of the effective regulatory rate (URAE-1 vs. 4^th cycle).

The average adjustment of 6.5% in the rate applied to users is calculated by applying inflation (i) and delta PIS COFINS (k).

São Paulo, December 2, 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: December 3, 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 rate adjustment did Sabesp (SBS) announce in this 6-K?

Sabesp announced that the regulator authorized a 10.6% increase in the equilibrium rate, reflecting updated costs, regulatory asset base remuneration, and prior-cycle compensatory adjustments.

How much will Sabesp (SBS) customers’ tariffs increase on average?

Sabesp estimates that the average tariff applied to users will increase by 6.5%, based on inflation (IPCA from July 2024 to October 2025) and the delta PIS COFINS effect.

What factors contributed most to Sabesp’s 10.6% equilibrium rate increase?

Key factors include lag in regulatory asset base recognition (3.54%), Opex (1.42%), market effects (3.41%), and inflation (6.11%), partially offset by a -5.37% compensatory adjustment from the 4th cycle.

How did the Alto Tietê PPP affect Sabesp’s rate calculation?

Sabesp notes that a main impact in non-manageable expenses is the end of rate coverage for the Alto Tietê PPP, reducing coverage by about R$130 million.

What time period does the inflation component in Sabesp’s adjustment cover?

The inflation component uses IPCA from July 2024 to October 2025, which is applied in the formula that leads to the total rate adjustment before and after taxes.

What is the role of delta PIS COFINS in Sabesp’s tariff adjustment?

The delta PIS COFINS of 0.36% updates the effective regulatory rate when comparing the URAE-1 contract to the 4th cycle, contributing to the final 10.65% total with taxes equilibrium adjustment.