What happened
SB 253, the Climate Corporate Data Accountability Act, was passed in 2023. CARB approved its first regulation on 26 February 2026 with a deadline of 10 August 2026, then withdrew the package in the summer and moved the deadline to 10 November 2026. It resubmitted the final package to California's Office of Administrative Law on 21 September. ESG Today reported on 15 October that the rules are now final, and CARB's programme page now states that 10 November 2026 is the deadline under the Initial Regulation. When we checked on 19 October, CARB's own rulemaking page had not yet posted the approval, so check it if the exact legal status matters to you.
The first-year rules are deliberately light:
- Only Scope 1 and Scope 2 are required. The regulation says in terms that Scope 3 is not required for 2026.
- Companies can send figures they already had or were collecting by 5 December 2024, or a letter saying they had no such data then. CARB will accept reports with or without third-party assurance this year.
- A parent company can report for its subsidiaries in one consolidated report.
Who is covered
A company is a "reporting entity" under SB 253 if all three of these apply:
- It is formed under US law: a US state, the District of Columbia or a federal act. CARB's FAQ says the law only applies to US-based companies.
- Its revenue is over US$1 billion, measured as gross receipts for California tax, using the lower of its last two financial years.
- It does business in California: it is organised or commercially domiciled there, or its California sales pass an inflation-adjusted threshold (US$735,019 for 2024, according to CARB's FAQ) or 25% of its total sales.
Both tests are applied company by company, not across a whole group. Charities, government bodies and insurance businesses are among those exempt.
What it means for a UK business
SB 253 puts no legal duty on a UK-registered company. How it reaches you depends on where you sit:
| You are | What happens |
|---|---|
| A UK supplier to large US companies | Nothing is required of you by law. From 2027 your US customers will have to report Scope 3, so expect questionnaires asking for your emissions, or your share of them. |
| A UK subsidiary of a US group that is covered | You don't report to CARB yourself. But Scope 1 and 2 under SB 253 count emissions "regardless of location", so if your sites are inside your group's reporting boundary, group finance will want your gas, fuel, refrigerant and electricity figures. |
| A UK group with a US subsidiary | Only that US subsidiary can be caught, and only if it passes the US$1 billion and California tests on its own. CARB's FAQ says a non-US parent can file a consolidated report for it voluntarily. |
Scope 3 from 2027: still being written
The law requires Scope 3 from 2027, but CARB is writing those rules in a second rulemaking that isn't finished. In its July 2026 workshop CARB staff proposed that companies first report five Scope 3 categories: purchased goods and services, fuel and energy related activities, waste, business travel and employee commuting, with the other ten voluntary. They also proposed that companies say what percentage of each category comes fromprimary data obtained from suppliers, while still allowing spend-based estimates. If that survives, it gives US customers a clear reason to ask you for real figures. Treat the detail as a proposal until CARB publishes final rules.
What to do now
- Have last year's Scope 1 and 2 ready. It's the first thing any customer asks for. CARB's proposals for 2027 build on the GHG Protocol standards, which UK frameworks use too.
- Know your share for each big customer. Many requests ask for emissions allocated to their account, as in the example below.
- Check your contracts. A supplier code or contract clause can oblige you to share data even though the law doesn't. Read our guide to answering a customer's carbon data request.
- Expect requests to arrive through platforms. Many US companies collect supplier data through CDP; see answering a customer's CDP supply chain request. Some will also ask whether you have a target; see what to do when a customer asks for a science-based target.
- If you have US sites, use US grid factors for them, not UK ones. Our US eGRID electricity factors by subregionlist them.
Worked example: your share for a US customer
Take a UK supplier with a 30,000 kWh electricity bill and 50,000 kWh of gas a year. With the 2026 UK government conversion factors that is 3.93 tCO2e of Scope 2 and 9.12 tCO2e of Scope 1, 13.04 tCO2e in all. If a US customer buys £400,000 a year from turnover of £2,000,000, its share by revenue is 20%, or2.61 tCO2e. That is the number that would sit in the customer's purchased goods and services category if it uses your figures. If it uses a spend-based estimate instead, your own cuts won't show in its report, which is one reason customers ask for real data.
How Carbon Recycling helps
Carbon Recycling turns your bills, fuel, travel and waste records into Scope 1, 2 and 3 figures with the right year's UK government factors, so you have one set of numbers for every customer request. Our free supplier questionnaire answer bank drafts model answers from those figures, including the revenue-share allocation for one customer. And once the share is visible, the reductions count: in this example, every tonne you cut from your own Scope 1 and 2 takes 20% of a tonne off what you report to that customer. For more on what large customers can and can't ask of you, see supplier carbon data requests.