California SB 253 Emissions Reports Due November 10

California's first corporate emissions reports are due November 10, 2026, and the filing is likely to be the lightest obligation the program ever imposes. The heavier work proposed for 2027, which adds independent assurance and the first slice of supply chain emissions, will be paid for out of budgets that many companies are cutting this month.

The deadline comes from Senate Bill 253 (SB 253), the Climate Corporate Data Accountability Act. It requires U.S. entities with more than $1 billion in annual revenue that do business in California to disclose Scope 1 and Scope 2 greenhouse gas (GHG) emissions every year, with Scope 3 value chain emissions added beginning in 2027. The California Air Resources Board (CARB) submitted its initial regulations to the state Office of Administrative Law (OAL) on May 20, 2026. CARB then withdrew the package on June 24, 2026, to make limited clarifying changes and announced that the first reporting deadline would move from August 10, 2026, to November 10, 2026. The finality of this new date depends on the OAL formalizing its approval of the revised rules.

CARB Will Accept Existing Data and Unassured Reports for 2026

CARB's guidance for 2026 submittals, dated September 1, keeps the first cycle deliberately loose. Under its December 2024 enforcement notice, the agency will accept prior fiscal year Scope 1 and Scope 2 figures based on information companies already had or were collecting. An existing annual report qualifies. So does data already filed with another program, or CARB's draft template. The statute calls for limited assurance starting in 2026, but CARB says it will take this year's submissions with or without it.

Companies that were not collecting emissions data as of December 5, 2024 are asked to send a statement of non-reporting on company letterhead. Reports and statements can go through a voluntary intake platform or by email. For Scope 2, companies may use EPA's Emissions & Generation Resource Integrated Database (eGRID) 2023 factors, or a 2024 dataset that the Cornerstone Sustainability Data Initiative built from the agency's public code, since the U.S. Environmental Protection Agency (EPA) has not released eGRID 2024 on its usual timeline. Companies are also invited to describe methodologies, boundaries and assumptions.

For sustainability teams working under a spending freeze, that flexibility is genuine relief. It carries a quieter consequence too. Whatever a company files in November becomes the public starting point for every later year, and auditors who open up corporate emissions data want to know how a number was built as much as what it says.

CARB Has Proposed Limited Assurance and Five Scope 3 Categories for 2027

At a July 21 public workshop, the agency previewed the second phase. Beginning with reports submitted in 2027, companies would need limited assurance from an independent third party over Scope 1 and Scope 2, according to a workshop summary from the law firm Akin Gump. Acceptable standards would include the American Institute of Certified Public Accountants' AT-C Section 210, International Organization for Standardization (ISO) 14064-3 and the International Standard on Sustainability Assurance (ISSA) 5000 for engagements beginning on or after December 15, 2026. The proposal would also keep November 10 as the annual deadline.

Scope 3 would start narrower than the 15 categories in the GHG Protocol. The pre-proposal requires five categories at first, covering purchased goods and services, fuel and energy related activities, waste generated in operations, business travel and employee commuting. For each, companies would describe their methods and exclusions and report how much of the total came from primary supplier data. Purchased goods and services leans hardest on suppliers, and companies have already seen Scope 3 figures take on legal weight beyond their value as data. None of this is final. CARB expects to release draft regulatory text later in 2026, followed by a 45-day comment period.

Data Behind 2027 Reports Is Being Generated Throughout 2026

Here is where a budget freeze bites. Each annual SB 253 report covers the company's prior fiscal year, so a calendar-year company filing in 2027 will be reporting on 2026. The utility bills, fuel records and supplier invoices an assurance provider would examine are accumulating now, under whatever controls exist today. Waiting for CARB's final text before funding data systems, supplier outreach or an assurance engagement letter does not shorten that window. It only leaves fewer months to fix what a reviewer finds.

Most of that spending is operating expense, so a capital freeze alone may not touch it. Broader cost holds often do. A request tied to a dated obligation, and sized against the data gaps the November filing exposes, is easier to defend in a budget review than a general sustainability line. Teams that have tracked how compliance exposure builds inside reporting systems will recognize the pattern.

Several things could still change the size of that request. OAL has to approve the revised initial regulation before November 10 carries legal force, and CARB's draft rules for 2027 will settle the final assurance and Scope 3 terms. Litigation is moving in parallel. The U.S. Court of Appeals for the Ninth Circuit has kept SB 261, California's companion climate risk disclosure law, on hold while the business groups' appeal proceeds, though that injunction does not reach SB 253. CARB has continued to expect reports by November 10, the same message companies heard when parts of the program paused earlier. The draft 2027 text, whenever it lands, is the document finance teams will want on the table before they lock next year's numbers.