Which California companies must report emissions by November 10, 2026

California's climate disclosure law is moving from preparation to compliance this month. The California Air Resources Board extended the deadline for companies' first greenhouse gas emissions reports to November 10, 2026—a three-month delay from the original August 10 date. SB 253, the Climate Corporate Data Accountability Act, requires certain large companies to start publishing their emissions data, marking the law's initial reporting cycle.

SB 253 is estimated to affect more than 5,000 large companies, though determining if your company qualifies requires checking specific criteria. CARB released implementation guidance in September 2026 that clarifies what reports must include, what formats are acceptable, and how much flexibility exists for companies handling their first disclosure.

Which companies must report

SB 253 applies to US-based business entities—partnerships, corporations, limited liability companies and other entities—with total annual revenues exceeding $1 billion that do business in California. Location of headquarters does not matter; if a company meets the revenue threshold and conducts business in the state, it must comply.

In September 2025, CARB published a preliminary list of roughly 4,160 entities that may fall under SB 253 or the related SB 261 law. Companies appearing on that list should treat it as a starting point, not a final determination. CARB has stated the list is not conclusive, so companies still need to assess their own obligations based on the law's criteria.

The threshold applies to annual revenues, whether a company earned them entirely in California or across the United States and internationally. If your company hits $1 billion in total annual revenue and does business in California, you likely qualify as a reporting entity.

What companies must report starting in 2026

For this first reporting cycle, companies must disclose Scope 1 and Scope 2 greenhouse gas emissions for their prior fiscal year. Scope 1 covers emissions a company produces directly—from its own facilities and vehicles. Scope 2 covers emissions from purchased electricity and other energy sources.

Companies must report their data following the Greenhouse Gas Protocol, an internationally recognized standard. Reports must be "easily understandable and accessible" through a digital platform operated by an emissions reporting organization, making the information public.

Beginning in 2027, companies will also need to report Scope 3 emissions, which cover a company's entire supply chain and value chain—upstream suppliers and downstream customers.

What CARB's September guidance clarifies

CARB released guidance on September 1 and 3, 2026 that addresses practical questions for companies preparing their first submissions. The guidance makes clear that companies do not need fresh data collection specifically for this report. Data companies already had, or were already collecting, as of CARB's December 5, 2024 enforcement notice can be used, whether from sustainability reports, internal systems, or prior voluntary initiatives.

Companies have flexibility in how they submit reports. Organizations can use existing annual reports, prior emissions disclosures to other programs, or CARB's draft template—no single format mandate exists. Submissions can go through CARB's voluntary reporting platform or via email. CARB also allows companies to choose emissions factor datasets and does not mandate a single source for calculating emissions from activity data.

For companies that lack emissions data collection infrastructure, CARB permits submission of a statement of non-reporting instead of GHG numbers. Companies must document their assessment process, but they can avoid submitting incomplete data if they did not have collection systems in place when the enforcement notice issued.

Third-party verification is optional for 2026. CARB will not require independent assurance of Scope 1 and 2 data in the initial reporting cycle, though companies should prepare for mandatory assurance beginning in 2027.

Enforcement and penalties for missing the deadline

The California Air Resources Board can impose administrative penalties for nonfiling, late filing, or other violations of SB 253 requirements. Penalties can reach a maximum of $500,000 per reporting entity per reporting year. However, CARB must evaluate a company's "past and present compliance" and "good faith measures" to comply when calculating penalties.

CARB has signaled it will exercise enforcement discretion during the first cycle. The board "will not take enforcement action against companies with incomplete reporting, provided they are acting in good faith," according to the September guidance.

The deadline is firm: companies must submit by November 10, 2026 to avoid potential penalties. Given that today is September 21, 2026, companies have just over seven weeks to prepare their first disclosures. Companies that have not yet determined whether they meet the revenue threshold or initiated data gathering should act immediately.

What comes next: Scope 3 and tighter assurance rules

In 2027, the law becomes more demanding. Scope 3 emissions reporting begins, requiring companies to track and disclose emissions throughout their supply chains and customer use of their products. This is far more complex than Scope 1 and 2, as it requires obtaining data from suppliers and partners who may not have that information readily available.

Assurance requirements also increase. From 2027 to 2029, Scope 1 and 2 data will require limited assurance from independent third parties—essentially a moderate level of verification by outside auditors. Beginning in 2030, reasonable assurance becomes mandatory for Scope 1 and 2, a higher standard. Scope 3 data will move to limited assurance beginning in 2030.

Between 2027 and 2030, a special protection applies to Scope 3 reporting. Penalties for good faith errors in Scope 3 data do not apply; companies face penalties only for failing to file Scope 3 data altogether. This safe harbor is intended to encourage good faith efforts as companies build the systems needed to collect emissions data from across their operations.