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___

March 16, 2026

SÃO PAULO, SP – Sabesp (SBSP3) reported adjusted earnings of R$3.93 per share in the 4Q25, compared to R$2.10 per share in the same period of the previous year.

“2025 was a year marked by ramp-up in capex deployment, capital structure and allocation discipline, and continued progress towards best-in-class operational efficiency. We invested R$15.2 bn, more than double the amount invested in 2024, and closed the year with Adj EBITDA of R$13.2 bn (+17% y/y) and Net Income¹ of R$6.3 bn (+22% y/y), results that reflect the aggregate effect of our efficiency plan.

In 4Q25, we kept pace and achieved important milestones where (i) collection rate reached 100.2%, (ii) costs declined by (11%) y/y, and (iii) volume grew by 3.0%, resulting in an Adj EBITDA of R$3.4 bn (+13% versus 4Q24) and Net Income¹ of R$1.9 bn,” said Daniel Szlak, CFO of Sabesp.

“More importantly, we´ve expanded the access to sanitation, meeting all U-Factor units incremental targets for 2024-25 one month ahead of schedule and brought water to 1,8 mn people and sewage to 3,8 mn people in that period. The magnitude of our investments also boosted the economy in the communities in which we operate, creating around 40,000 direct and indirect jobs.

As the largest sanitation company in the Southern Hemisphere, we remain committed to an agenda that combines top-notch infrastructure investment, operational excellence and sustainability in our communities. We enter 2026 with even stronger foundations to accelerate this movement,” said Carlos Piani, CEO of Sabesp.

Consolidated Results

For the quarter-ended December 31, 2025, Sabesp reported adjusted earnings per share of R$3.93 compared to R$2.10 recorded in the same period of the previous year. Performance was driven by volume growth resulting from new connections (U-Factor targets fully attained), tariff gains and better collection, partially offset by the change in customer mix, with the expansion of connections with access to subsidized rates².

The quarter maintained the momentum of efficiency gains, with reductions in general and administrative expenses, headcount reduction, power optimization with shifts to the free market, and a lower allowance for doubtful accounts. These factors contributed to a 13% gain in Adj EBITDA, totaling R$3.4 bn in 4Q25, and offset the effect of higher benchmark rates (Selic) in financial expenses to maintain Net Income stable at R$1.9 bn y/y.

Sabesp invested R$4.8 bn in 4Q25, a 73% increase over the same period of the previous year, focusing on expansion projects directly aimed at meeting universalization targets.

Earnings Conference Call

Will be held on March 17, 2026, at 10:00 AM (Brasília time). Access link is available at the Company’s Investor Relations website. The presentation has been made available at the same website. An audio recording of the call will be posted at the same website.

ADJUSTED INCOME STATEMENT (CONSOLIDATED)

4Q25

R$ mn

Balance adjusted by construction revenue/cost

The non-recurring effects on 4Q25 EBITDA were: (i) R$ 369 mn related to tax credits; (ii) R$ (60) mn in accruals for logistics restructuring and (iii) R$ (28) mn reduction in legal contingencies.

For comparison purposes, the non-recurring impacts reported in 4Q24 EBITDA were: (i) Sabesp Gente VTP accrual for R$ 630 mn; (ii) reassessment of legal claims R$ 471 mn; (iii) Write-off of work in progress fixed assets of R$ 164 mn; (iv) R$ 111 mn of accrual for taxes on unbilled revenue; (v) R$ 100 mn of Privatization expenses; (vi) Slow move and inventory difference accrual of R$ 95 mn; and (vii) Post-privatization PMI consulting of R$ 40 mn.

In addition to the impact of non-recurring items on 4Q25 EBITDA, there was a non-recurring effect of R$ 154 mn in financial results, related to the monetary update of tax recoveries.

2025

R$ mn

ADJUSTED NET REVENUE

Adjusted net revenue from sanitation services, considering FAUSP and taxes, totaled R$ 5,682 mn in 4Q25, an increase of +2.1% vs 4Q24. The main factors that impacted revenue in the period were:

For the year, revenue growth was 2.2%, R$ 487 mn higher vs 2024, with the main factors being:

CONSUMPTION BY CATEGORY

(1) Others are composed of Public, Own Building, and Mauá (BRK).

(1) Active and registered connections, average at the end of the period

Not audited by external auditors

COST AND EXPENSE

In 4Q25, OPEX showed a 10% reduction vs 4Q24, a decrease of R$ 267 mn. The main factors for this result were: (i) R$ 172 mn in general and administrative expenses, composed mainly R$ 152 mn of municipal funds (FMSAI) anticipation; and (ii) R$ 86 mn in personnel reduction in headcount, partially offset by services logistics investments, environmental compensation and IT. For the full year, the reduction was 13% vs 2024, with costs and expenses totaling R$ 9,041 mn.

R$ mn

PERSONNEL

Sabesp ended 4Q25 with 8,717 employees, a 17% reduction vs the same period of the previous year,

capital expenditures

In 4Q25, CapEx totaled R$ 4,771 mn, an increase of 73% compared to 4Q24 and 20% compared to 3Q25, in 2025, CapEx totaled R$ 15,202 mn, an increase of 120% compared to the same period of the previous year,

R$ mn

BALANCE SHEET (CONSOLIDATED)

STATEMENT OF CASH FLOWS (CONSOLIDATED)