California Air Resources Board Holds Public Workshop on Emissions Reporting under SB 253 Beginning in 2027

On July 21, 2026, the California Air Resources Board (“CARB”) held a public workshop regarding the development of California’s corporate greenhouse gas reporting program under Senate Bill 253.[1] This is CARB’s fifth public workshop on its rulemaking to implement California’s climate reporting laws[2] and the second public workshop in its pre-rulemaking process regarding greenhouse gas (“GHG”) reporting requirements for reports due beginning in 2027, ahead of a formal rulemaking process to occur later in 2026.

At this workshop, CARB staff also provided an update on the initial regulation implementing the climate reporting laws (the “Initial Regulation”), which had set an August 10 reporting deadline for GHG reports due in 2026. The Initial Regulation, including the August 10 deadline, is not currently effective. CARB staff noted that the Initial Regulation will be reproposed with “limited further clarifying changes,”[3] and will require GHG reports due in 2026 to be submitted by November 10. CARB staff further noted that they will provide additional guidance materials to support 2026 reporting “by September 1, 2026.”

Both SB 253 and SB 261 remain subject to ongoing litigation. As of the date of this publication, CARB has temporarily halted the enforcement of SB 261, which had a statutory initial reporting deadline of January 1, 2026, as a result of an injunction pending appeal by the U.S. Court of Appeals for the Ninth Circuit, while in-scope entities remain obligated to submit their initial reports under SB 253 by CARB’s reporting deadline.

Key Updates on SB 253 Reporting in 2026

Delayed 2026 Reporting Deadline. CARB staff provided a brief update on the process for proposing and formal adoption of an updated regulatory package for the Initial Regulations applicable to reports due in 2026, including its proposal to update the initial GHG reporting deadline to November 10, 2026 in order to give reporting entities additional time following the formal adoption of the updated regulatory package. CARB did not specify when this updated regulatory proposal will be released, but noted that the proposal will be “available for comment as part of a forthcoming 15-day public comment period,” which “may delay finalizing [the updated] regulatory package.” CARB also did not specify the “limited further clarifying changes” it will propose as part of the updated regulatory proposal.[4]

Additional Guidance Materials. In addition to updating the Initial Regulation, CARB announced plans to share “additional guidance materials” to support 2026 GHG reporting by September 1, 2026. CARB staff noted that these materials will include a voluntary online intake platform for fee contact information and GHG emissions reporting, as well as an accompanying guidance document and instructional video.[5] During the Q&A session, CARB staff noted that they expect to launch the submission portal for 2026 reports by September 1, 2026 

Key Proposed Concepts for SB 253 Reporting Beginning in 2027

Reporting Deadline. Rather than imposing a staggered deadline for Scope 1, 2 and 3 emissions, CARB staff noted that they plan to propose an annual reporting deadline of November 10 for all required emissions disclosures.

Insurance Companies. The previously approved Initial Regulation exempted insurance companies from 2026 GHG reporting to avoid duplication with GHG reporting requirements imposed by the California Department of Insurance (“CDI”). At the workshop, CARB staff noted their finding that CDI reporting requirements may not satisfy the requirements of SB 253 beginning in 2027, as CDI requirements do not include Scope 3 or assurance requirements. Therefore, beginning in 2027, CARB staff proposes that insurance entities may submit the same report to satisfy both the CDI and SB 253 reporting requirements so long as the report meets the requirements of SB 253. Otherwise, the insurance entity must supplement its CDI report with the remaining required information under SB 253.[6]

General Requirements. In response to public feedback on the previous public workshop, CARB staff stated that they plan to propose regulatory language “to implement the broader directives in SB 253, and/or meet the requirements of California administrative law.”[7] CARB staff further noted that they would implement GHG Protocol requirements with “appropriate clarity and specificity” and will propose general requirements for GHG reporting across Scope 1, 2 and 3 emissions, including:

• Quantification Methodologies. Companies would be required to disclose the GHG quantification methods and measurement approaches used for the calculation of all emissions in their SB 253 reports, including consolidation approach for organizational boundaries, Global Warming Potential values and assessment report vintage, emission factor sources for all calculations with key attributes, and quantification method (e.g., direct measurement or calculation-based method), including any process-specific tools or models used.[8]
• Measurement Uncertainty. Companies would be required to assess the uncertainty associated with the quantification methodologies used to calculate emissions, including a quantitative explanation where applicable. Where quantitative estimation of uncertainty is not feasible or would impose unreasonable burden or cost, the company must provide an explanation and conduct a qualitative assessment of uncertainty.[9]
• Missing Data Protocols and Substitution Procedure. Companies would be required to identify missing data elements or parameters and document any substitute data sources or estimation methods used to quantify emissions in place of the missing data.[10]
• Reporting Biogenic Emissions. CARB staff previewed draft regulatory language that would require companies to report biogenic CO₂ emissions from the combustion, consumption or biodegradation of biomass andbiomethane in their SB 253 reports, and for such emissions to be reported separately from Scope 1, 2 and 3 emissions totals.[11]
• Reporting Emissions Reductions or Removals. Companies may report voluntary investments (e.g., carbon credits, offsets), management activities or other activities that result in fossil or biogenic emissions reductions or removals. These voluntary investments or management activities must be reported separately from Scope 1, 2 or 3 emissions.[12]
• Data Exclusions. Companies would be permitted to exclude GHG emissions sources, activities, Scope 3 categories or other information “where the omission, misstatement, or obscuring could not be reasonably expected to influence the decisions, assessments, or understanding of users of the disclosure regarding the reporting entity’s GHG emissions inventory, climate-related risks, opportunities, or impacts.” CARB is currently planning to propose requiring companies to assess data exclusions using both quantitative and qualitative factors, and to explain and disclose the basis for all data exclusions. For each category, source, facility, operation, or disclosure excluded, the company would also be required to disclose an estimate of the emissions magnitude of exclusions, if quantifiable.[13]
• Notifying CARB of Changes to Methodologies. In annual GHG reports, companies would be required to include disclosures of changes to GHG quantification or accounting methods made from the previous reporting year or during the current reporting period, and the reasons for those changes.[14]
• Recalculation of Previous Year Data. Companies that change their GHG emissions calculation methodologies (including for corporate structuring or accounting reasons) would be required to determine whether the cumulative effect of all structural and methodological changes would result in a change greater than 5% of their total GHG emissions for the base year (i.e., their first reporting year under SB 253). If so, the company must recalculate the reported emissions for all affected previous reporting years, and the updated emissions data for those years must be included in the next annual GHG emissions report along with a description of the changes that led to the recalculation.[15]

CARB is seeking feedback on various aspects of these proposed general requirements, including how to encourage reporting entities to “apply the most scientifically sound approach for emissions quantification.” For example, CARB has asked for feedback on specific measurement approaches, emission factors or quantification methods that it should encourage or require.[16]

Specific Requirements for Scope 2 Reporting. Companies would be required to disclose Scope 2 emissions by source type, by constituent gas, and use both market-based and location-based methods.[17]

Specific Requirements for Scope 3 Reporting. CARB staff noted that it received feedback from stakeholders that assessing all 15 Scope 3 categories beginning in 2027 could pose data availability and cost challenges.[18] As a result, CARB staff proposes requiring reporting on the five “most commonly-reported” categories, starting in 2027: purchased goods and services (Category 1), fuel and energy related activities (Category 3), waste generated during operations (Category 5), business travel (Category 6) and employee commuting (Category 7). Companies would be permitted, but not required, to report emissions from the other 10 categories, particularly for entities already reporting additional categories to other jurisdictions.[19] Companies would also be required to disclose detailed information for each Scope 3 category, including the activities included in the emissions inventory and the percentage of emissions calculated using primary data.[20] Notably, CARB staff emphasized during the Q&A session that notwithstanding the forthcoming Scope 3 reporting requirements, the statutory text for SB 253 provides that “[p]enalties assessed on scope 3 reporting, between 2027 and 2030, shall only occur for nonfiling.”

Proposed Assurance Requirements. CARB reiterated that companies will be required to obtain limited assurance for Scope 1 and 2 emissions reports beginning in 2027.[21] CARB staff is currently planning to propose the following list of assurance standards that would be acceptable for use in connection with SB 253 reporting:

• AA1000 Assurance Standard (AA1000AS v3);
• American Institute of Certified Public Accountants (AICPA AT-C Section 210);
• International Standard on Assurance Engagements (ISAE) 3410 applied in conjunction with ISAE 3000 (Revised), for engagements commencing prior to December 15, 2026;
• International Standard on Sustainability Assurance (ISSA) 5000 for engagements commencing on or after December 15, 2026; or
• International Organization for Standardization (ISO) 14064-3:2019 (with additional accreditation requirements).

The assurance provider would be required to issue and submit a written report that identifies the assurance standard applied and the level of assurance provided, the Scope 1 and Scope 2 emissions covered by the engagement, the legal name of the organization that conducted the assurance engagement and contact information for the assurance provider.[22] 

Next Steps

Upcoming Regulatory Proposals. In addition to the proposed update to the Initial Regulation discussed above, CARB staff noted that it will release, later this year, a proposed regulation for GHG emissions reporting under SB 253 beginning in 2027 (the “Subsequent Regulation”).

Comment Periods. CARB did not provide a comment period for feedback on the concepts presented at this workshop. According to CARB, when it releases the proposed Subsequent Regulation, the public will have a 45-day comment period before the proposed regulation is submitted for CARB board approval.   

Listening Sessions. CARB announced a series of six scheduled “listening sessions” between August 5, 2026 and September 9, 2026. CARB intends to use these sessions to gather feedback from different sectors, including (1) data users and public interest stakeholders, (2) manufacturing, industry, fuel and life sciences, (3) agriculture, food, beverage and forestry, (4) energy, utilities, transportation, logistics and waste management, (5) retail, consumer goods, technology and commercial services, and (6) banking, finance and insurance.[23] Interested persons can sign up for updates on these sessions here.