California has released additional guidance for the first reporting cycle under Senate Bill 253 (SB 253), providing companies with more clarity on what they need to submit, how they can submit it, and how the California Air Resources Board (CARB) plans to approach enforcement in 2026.

The key takeaway is that the November 10, 2026 reporting deadline remains in place, but CARB is maintaining a flexible first-year approach. The agency has also launched a voluntary reporting platform designed to simplify submissions and fee administration.

What Companies Need to Know for the 2026 Filing

SB 253 requires covered companies to disclose their Scope 1 and Scope 2 greenhouse gas (GHG) emissions for the preceding fiscal year. The law generally applies to U.S.-organized business entities with more than $1 billion in total annual revenue that do business in California.

CARB's September 1 guidance confirms that reports for the first reporting cycle are due by November 10, 2026. Importantly, the new guidance does not create additional substantive reporting obligations. Instead, it explains how CARB intends to administer the first year of the program and exercise previously announced enforcement discretion.

CARB Maintains a Flexible First-Year Enforcement Approach

For 2026, CARB continues to rely on the enforcement approach it first announced in December 2024.

Companies may submit Scope 1 and Scope 2 emissions using information they already had, or were already collecting, when CARB issued its December 2024 Enforcement Notice. CARB will also accept 2026 submissions regardless of whether the emissions data has received limited assurance, even though SB 253 otherwise contemplates limited assurance beginning with the 2026 reporting cycle.

Companies that were not collecting, and were not planning to collect, Scope 1 or Scope 2 data as of December 5, 2024 are not expected to provide emissions data for this first reporting cycle. CARB instead recommends that these companies submit a statement on company letterhead explaining that they were not collecting or planning to collect the relevant data at that time.

This flexibility applies specifically to the 2026 transition year and should not be interpreted as the reporting standard CARB intends to apply going forward.

Several Reporting Formats Will Be Accepted

Companies do not need to create a completely new California-specific sustainability report for 2026. CARB identifies several acceptable approaches, including:

• submitting an existing annual or sustainability report containing Scope 1 and Scope 2 emissions;

• submitting emissions information already reported through another regulatory or voluntary program;

• using CARB's draft Scope 1 and Scope 2 reporting template; or

• where applicable, submitting a statement of non-reporting explaining that the company was not collecting or planning to collect the relevant emissions data as of December 5, 2024.

CARB also encourages companies to provide supporting information where available, including calculation methodologies, emissions factors, data sources, organizational boundaries and assumptions. These additional details can help explain how the reported emissions figures were developed, although the guidance distinguishes these encouraged disclosures from the core annual Scope 1 and Scope 2 emissions figures.

A New Voluntary Reporting Platform Is Now Available

CARB has also launched a voluntary intake platform for the 2026 reporting cycle.

Companies can use the platform to submit emissions reports, provide contact and billing information, or submit a statement of non-reporting. Use of the platform itself is not mandatory. Companies may instead submit their emissions information directly to CARB by email.

The platform also allows a company to make a single submission on behalf of multiple reporting entities. This could be particularly useful for multinational corporate groups where several subsidiaries independently qualify as reporting entities but rely on a consolidated corporate emissions inventory. Companies can also indicate whether fees should be paid together or separately for the individual reporting entities.

One consideration is transparency. CARB has indicated that both emissions reports uploaded through the platform and statements of non-reporting will be made public.

CARB Provides Flexibility on Scope 2 Emissions Factors

CARB also addressed uncertainty surrounding the emissions factors companies may use when calculating Scope 2 emissions, which generally relate to emissions associated with purchased electricity and other acquired energy.

For 2026, CARB is not requiring companies to use a specific emissions factor dataset. Companies may use the U.S. Environmental Protection Agency's most recent official Emissions & Generation Resource Integrated Database, known as eGRID 2023, or the 2024 dataset published by the Cornerstone Sustainability Data Initiative using EPA source code. Other credible emissions factor sources may also be used.

CARB encourages companies to identify which emissions factors and sources they relied upon.

What Companies Should Be Doing Now

With the November 10 deadline approaching, companies that may fall within SB 253 should now be moving from applicability analysis into filing preparation.

Key near-term priorities include confirming which legal entities within the corporate group are independently subject to SB 253, determining which prior fiscal-year emissions information is available, deciding whether an existing sustainability or emissions disclosure can be used for the filing, and documenting the methodologies and organizational boundaries underlying the reported numbers.

Companies should also determine whether they will use CARB's voluntary platform and coordinate how submissions will be handled where multiple subsidiaries are potentially subject to the law.

For companies relying on CARB's first-year enforcement discretion because they were not collecting emissions information in December 2024, preparing the recommended statement of non-reporting ahead of November 10 will be particularly important.

The Bigger Picture: 2027 Will Look Different

The comparatively flexible 2026 approach should not be viewed as the permanent SB 253 compliance model.

CARB is developing a second rulemaking covering reporting from 2027 onward. That process is expected to address greenhouse gas accounting methodologies, future reporting deadlines, assurance requirements and reporting formats.

For companies subject to SB 253, the 2026 filing therefore represents both a compliance deadline and a transition year. Organizations can use this first cycle to establish stronger emissions governance, reporting boundaries, documentation and assurance processes before CARB's more standardized requirements begin to take shape.