SB 253: What every supplier to US companies needs to know in 2025
California's Climate Corporate Data Accountability Act is reshaping what large US companies must report — and that means asking their suppliers for emissions data.
California Senate Bill 253 — the Climate Corporate Data Accountability Act — is one of the most significant climate disclosure laws ever enacted. Signed into law in October 2023, it requires companies with over $1 billion in annual revenue doing business in California to publicly disclose their greenhouse gas emissions — including Scope 3 emissions from their entire supply chain.
Who is covered by SB 253?
SB 253 applies to any US or non-US company that:
- •Has annual revenues exceeding $1 billion, AND
- •Does business in California
"Doing business in California" is broadly interpreted. If a company has employees, customers, or operations in California — or if it sells products or services to California residents — it is likely covered.
The California Air Resources Board (CARB) estimates that approximately 5,300 companies are covered by SB 253. These include some of the world's largest companies — and their supply chains extend to hundreds of thousands of smaller businesses around the world.
What does SB 253 require?
Covered companies must publicly disclose their greenhouse gas emissions in line with the GHG Protocol Corporate Standard:
Scope 1 & 2 emissions
First reports due August 2026 (covering FY 2025 data)
Scope 3 emissions (including supply chain)
First reports due 2027 (covering FY 2026 data) — this is where your data comes in
What does this mean for you as a supplier?
If any of your customers are US companies with over $1 billion in annual revenue doing business in California, they will need your emissions data to complete their SB 253 Scope 3 report. Specifically, they will need:
- •Your Scope 1 emissions (direct emissions from your operations)
- •Your Scope 2 emissions (emissions from your purchased electricity)
- •Your calculation methodology and emission factors used
- •Whether your data has been verified by a third party
How to prepare
Calculate your GHG footprint
Start with Scope 1 and 2 emissions. Collect your energy bills, fuel records, and refrigerant data. Use DEFRA (UK), EPA (US), or IEA emission factors to convert activity data to CO2e.
Document your methodology
Record which emission factors you used, which reporting boundary you applied (operational control, equity share, or financial control), and which GHG Protocol guidance you followed.
Consider third-party verification
SB 253 requires third-party assurance for Scope 1 and 2 emissions. Buyers may request verified data from their suppliers. ISO 14064-3 provides the standard for GHG verification.
Build your evidence library
Store your GHG calculations, methodology documentation, and supporting data in a central location. ESG Stress Free provides a document library and GHG tracking tool for this purpose.
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Free SB 253 supplier checklist
Download our step-by-step guide to preparing your emissions data for US buyer requests.