Protect your business, meet assurance requirements and report with confidence.
Learn More About Verification
California's Climate Corporate Data Accountability Act (SB 253) is the first law in the United States to require large companies to publicly report their full greenhouse gas emissions and to have that data independently assured.
With the first Scope 1 and Scope 2 reports due on 10 November 2026, and third-party assurance requirements tightening from the 2027 reporting cycle onwards, companies doing business in California need emissions data that will stand up to regulatory scrutiny.
Carbonology provides the independent and accredited verification you need to report with confidence and meet the requirements of SB 253.
The Climate Corporate Data Accountability Act (SB 253) was signed into law in October 2023 and later amended by SB 219. It requires U.S.-based companies with more than $1 billion in total annual revenue that do business in California to measure and publicly disclose their greenhouse gas emissions. The California Air Resources Board (CARB) is responsible for implementing and enforcing the law.
The law applies regardless of where in the U.S. a company is headquartered. If you meet the revenue threshold and do business in California, you are likely in scope, including subsidiaries and privately held companies.
The law's purpose is to give investors, customers, regulators and the public consistent, reliable and comparable emissions data. Independent assurance is the mechanism that makes that data trustworthy.
SB 253 introduces the following obligations:
Scope 1 and Scope 2 Reporting: Report direct emissions from owned or controlled sources (Scope 1) and indirect emissions from purchased electricity, steam, heating and cooling (Scope 2), beginning in 2026.
Scope 3 Reporting: Report indirect value chain emissions, including purchased goods and services, business travel, transportation, use of sold products and more, beginning in 2027.
GHG Protocol Alignment: Emissions must be calculated and reported in line with the GHG Protocol Corporate Accounting and Reporting Standard and Scope 3 Standard.
Independent Third-Party Assurance: Emissions data must be assured by an independent provider. Limited assurance applies to Scope 1 and 2 first, moving to reasonable assurance from 2030. Limited assurance on Scope 3 follows from 2030.
Public Disclosure: Reports are submitted to CARB and made publicly available, putting your emissions data in front of investors, customers, NGOs and competitors.
Scope 1 and 2: Limited assurance from the statute's first reporting year, with CARB accepting 2026 submissions with or without assurance. CARB is proposing mandatory limited assurance from the 2027 reporting cycle. Reasonable assurance is required from 2030.
Scope 3: Reporting begins in 2027, with limited assurance required from 2030.
October 2023: SB 253 signed into law
2026: First reporting year for Scope 1 and Scope 2 emissions
10 November 2026: First Scope 1 and 2 reporting deadline
2027: Scope 3 reporting begins, and mandatory limited assurance for Scope 1 and 2 is proposed
2030: Reasonable assurance required for Scope 1 and 2, and limited assurance required for Scope 3
The law applies to any U.S. entity with more than $1 billion in total annual revenue doing business in California, regardless of where the company is incorporated or headquartered.
Non-compliance with SB 253 carries real risks:
Financial Penalties: CARB can impose administrative penalties of up to $500,000 per reporting year for non-compliance.
Public Scrutiny: Because reports are publicly available, errors, inconsistencies or gaps in your emissions data are visible to investors, customers, journalists and activists.
Litigation Risk: Inaccurate or unsupported disclosures can expose companies to claims from shareholders, competitors and advocacy groups.
Reputational Damage: Poorly substantiated data, or failure to report at all, can damage stakeholder trust and your standing with customers and investors.
Understanding SB 253 Verification | Watch the Video. (2.5mins)
Our accredited verification gives you confidence that your emissions disclosures are accurate, complete and ready for regulatory and public scrutiny.
Our core verification services include:
Scope 1 and 2 Verification: Independent verification of your direct and energy-related emissions, providing the foundation for your SB 253 report. Conducted in accordance with ISO 14064-3 and aligned with the GHG Protocol.
Scope 3 Verification: Verification of your value chain emissions, including data quality, methodology, boundary and completeness, so you are prepared as Scope 3 reporting and assurance requirements phase in.
Limited and Reasonable Assurance: Assurance engagements designed to meet current requirements and scalable to the higher level of assurance required from 2030.
Before your report is due, we offer a comprehensive readiness assessment:
Scope and Boundary Review: Confirmation of your reporting entity, organisational boundary (operational control, financial control or equity share) and consolidation approach.
Data and Evidence Review: Evaluation of data quality, calculation methodology, emission factors and supporting documentation, to identify gaps before assurance begins.
Controls and Process Review: Assessment of the systems, controls and governance behind your GHG data, and where they need to be strengthened.
Remediation Recommendations: Practical, prioritised guidance to close gaps and get your inventory assurance-ready.
We help you build consistency across your climate disclosures so you verify once and use the results many times:
Regulatory Compliance
Meet SB 253's assurance requirements with independent, accredited verification. Demonstrate good faith and due diligence to CARB and other stakeholders.
Risk Reduction
Reduce the risk of penalties of up to $500,000 per reporting year, and the risk of errors or unsupported figures entering the public record.
Brand Protection
Your emissions data will be public. Verified data protects you from greenwashing allegations, media scrutiny and challenges from advocacy groups.
Investor and Customer
ConfidenceVerified emissions data builds trust with investors, lenders, customers and supply chain partners who increasingly expect assured information.
Operational Efficiency
Verify once and use the results across SB 253, CDP, CSRD, ISSB, EcoVadis and customer requests. Build audit-ready systems that serve multiple purposes.
Future-Proofing
Build data systems and internal controls now that will support the move to Scope 3 reporting and reasonable assurance in 2030, and any further climate disclosure requirements.
1. Confirm Whether You Are in Scope
Check whether your organisation exceeds the $1 billion revenue threshold and does business in California, including subsidiaries and related entities. Confirm which entity or entities must report.
2. Define Your Reporting Boundary
Decide on your consolidation approach (operational control, financial control or equity share) in line with the GHG Protocol, and apply it consistently across reporting years.
3. Complete Your Scope 1 and 2 Inventory
Calculate your emissions using recognised methodologies and appropriate emission factors, and document the data sources, assumptions and calculations behind your figures.
4. Get a Pre-Verification Gap Analysis
Identify data quality issues, missing evidence and control weaknesses before an assurance provider does. Fixing gaps early is faster and cheaper than fixing them under deadline pressure.
5. Engage Independent Verification
Work with an accredited verification body like Carbonology to obtain assurance over your emissions data. Even where assurance is not yet enforced for your first submission, starting now avoids a scramble when it becomes mandatory.
6. Prepare for Scope 3
Begin mapping your value chain, engaging suppliers and identifying your most material Scope 3 categories now, ahead of 2027 reporting and assurance from 2030.
7. Establish Governance and Controls
Assign clear ownership for emissions data, build review and approval workflows, and keep audit trails so that your reporting can be repeated, reviewed and assured year after year.
Accredited Independence: Our verification body is accredited to ISO 14065 / ISO 17029 and operates with complete independence, providing assurance that meets regulatory expectations and withstands scrutiny.
Standards Expertise: Deep experience with ISO 14064-3, the GHG Protocol, ISAE 3000 and ISAE 3410, and other recognised assurance standards.
Cross-Regulatory Expertise: We understand how SB 253 intersects with SB 261, CSRD, ISSB, CDP and other frameworks, helping you build one joined-up approach.
Practical, Business-Focused Approach: Actionable recommendations that get you assurance-ready without unnecessary complexity.
Proven Track Record: Extensive experience verifying GHG emissions and sustainability reporting for organisations across diverse sectors.
Timely Support: We understand the pace of the SB 253 timeline and are ready to help you get ready efficiently.
Get SB 253-Ready with Carbonology Don't wait until assurance becomes mandatory. Contact Carbonology today for a confidential conversation about your emissions data and verification needs. Our team will help you understand your obligations, identify gaps and build a clear roadmap to SB 253 readiness.
Which standard do you need help with?
ISO 14064-1 / ISO 14064-3 Verification / GHG Protocol / Scope 3 emissions reporting / Supplier surveys and reports / SB 253 Gap Analysis / Other carbon management support
