Last updated: October 2026
California Senate Bill 253 (SB 253), also known as the “Climate Corporate Data Accountability Act,” was signed into law in October 2023 by California Governor Newsom, marking a crucial moment in the establishment of mandatory emissions reporting legislation on the state level.
CA SB 253 is one of two separate bills of the Climate Accountability Package – SB 253 and SB 261 – which both aim to improve and increase corporate transparency.
Focusing on SB 253, here we outline highlights of this historic bill, what organizations it impacts, and what you can do to prepare for it. Note: the first SB 253 report is due November 10, 2026!
WHAT DOES SB 253 REQUIRE?
The Climate Corporate Data Accountability Act (SB 253) applies to both public and private companies that do business in California and whose total annual revenues exceed $1 billion globally, not just in California. After undergoing amendments, the final law mandates annual reporting of emissions from all scopes: direct emissions (Scope 1), emissions associated with purchased electricity, steam, heat, and cooling (Scope 2), and indirect emissions linked to value chains (Scope 3). Companies should assess applicability at the entity level using CARB’s adopted regulatory definitions of revenue and doing business in California.
Companies below the threshold with plans for growth should also begin preparing. Business emissions inventories and data management processes now can support future compliance and demonstrate to investors that the company is planning for the reporting responsibilities that come with growth.
These rules will be rolled out over time, starting with the first SB 253 report due November 10, 2026, with Scope 1 and 2 emissions being mandated in 2026, and Scope 3 emissions being mandated in 2027. Reports must adhere to Greenhouse Gas Protocol (GHG Protocol) standards for measurement and reporting. Detailed requirements for 2027 and later reporting, including Scope 3 implementation and assurance, are being developed through separate rulemaking.
CARB released first-year reporting guidance on September 1, 2026, and the Initial Regulation took effect following Office of Administrative Law (OAL) approval on October 12, 2026. Key details for 2026 reporting include:
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- Reports cover the applicable entity’s prior fiscal year ending in 2025. Companies should confirm the reporting period against their fiscal calendar using CARB’s 2026 guidance.
- Disclosure is due November 10, 2026.
- Under its first-year enforcement discretion, CARB will accept 2026 submissions whether or not limited assurance was obtained. This flexibility does not remove the law’s assurance provisions; requirements for subsequent reporting cycles are being addressed through rulemaking.
- Companies may submit an existing annual report containing Scope 1 and 2 emissions, data already reported to other programs or voluntary initiatives, or CARB’s voluntary draft reporting template.
- For this first cycle only, entities that were neither collecting nor planning to collect Scope 1 and 2 information as of December 5, 2024, are not expected to submit emissions data. CARB asks these entities to submit a statement of non-reporting on company letterhead by November 10, 2026.
- Submit reports or statements of non-reporting through CARB’s voluntary 2026 Report Intake Platform or by email to [email protected]. The platform is optional; the underlying reporting obligation is not. Emissions reports and statements of non-reporting will be made public.
- CARB plans to send annual fee invoices by December 10, 2026, with payment due within 60 calendar days of the invoice notice date.
For more information, check out CARB’s 2026 reporting guidance.
WHAT CAN I DO TO PREPARE?
SB 253 represents a significant step toward comprehensive emissions reporting, with far-reaching implications for corporate accountability in addressing climate change. Thousands of companies doing business in California will need to disclose their Scope 1, 2, and 3 greenhouse gas emissions in the coming years. Companies will need to be confident in their reporting and have data management structures in place to assist with emissions reporting and verification.
We recommend that companies:
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- Develop a comprehensive GHG inventory inclusive of your operations and value chain emissions (Scope 1, 2, and 3). Prioritize the applicable submission for the November 10 deadline, while continuing to build Scope 3 readiness.
- Establish a data management framework for your data to prepare for assurance.
- Monitor upcoming developments with CA SB 253. Scope 3 phase-in concepts discussed by CARB remain proposals until finalized through rulemaking.
- Consider assurance of emissions to strengthen data quality and prepare for future reporting requirements. CARB will accept 2026 submissions with or without assurance under its first-year enforcement flexibility. Assurance requirements for subsequent reporting cycles remain subject to CARB’s ongoing rulemaking. Stok recommends starting with limited assurance and working toward reasonable assurance at a future date:
- Limited assurance is the baseline level of assurance where an auditor does a review to state they are not aware of material modifications that should be made.
- Reasonable assurance is a higher level of assurance and is more rigorous and intensive, which requires evidence to demonstrate the reporting is free of significant misstatements.
HOW DOES THIS STATE LAW ALIGN WITH GLOBAL LEGISLATION?
Covering both private and public companies, California’s legislation stands out as climate-related regulation accelerates globally. Internationally, more than 33 countries are in the process of setting disclosure standards aligned with the International Sustainability Standards Board (ISSB)’s IFRS S1 and S2. State-level action is advancing too, with states such as New York introducing climate data accountability legislation closely aligned with California’s. Moving forward, we will continue to see a shift from voluntary reporting to regulated requirements, requiring a risk-based, future-ready approach to turn compliance into competitive advantage.
The Stok team is here to help you understand CA SB 253 requirements and prepare for emissions disclosures wherever you are on your climate journey. For an overview of its companion law focused on climate-related financial risk, explore our guide to SB 261. Reach out to discuss with our carbon experts.
