SB 253 Is Final: What the 10 November Reporting Deadline Means for Your 2027 Scope 3 Plan

For months, the question in many US subsidiaries of European groups was whether the California deadline would slip again. It did once: the first reporting date moved from 10 August to 10 November 2026. With the regulation now approved, that question is closed. If your company is in scope, you have weeks, not months.

We covered the earlier stage of this rulemaking in what CARB's February 2026 approval means for your compliance timeline. This update covers what changed on 12 October and what to do next.

What did California finalise on 12 October 2026?

The Office of Administrative Law approved CARB's Initial Regulation implementing SB 253 and SB 261, and it took effect the same day. The rules are codified at Title 17, California Code of Regulations, sections 96070 to 96077.

Three points stand out:

• The deadline is fixed. The approval "formally establishes November 10, 2026 as the first-year reporting deadline under Senate Bill 253".
• The regulation defines applicability. It sets out key concepts for deciding who is covered under SB 253 and SB 261, and introduces an annual fee framework
• The history matters. CARB first approved the regulation on 26 February 2026, then withdrew it from review, which pushed the first deadline from 10 August to 10 November 2026 (same source).

Who must file by 10 November 2026?

Companies with more than USD 1 billion in annual revenue that do business in California, subject to the regulation's definitions and exemptions. The revenue threshold refers to total revenue, not California revenue alone.

For chemical, automotive and food groups headquartered in Europe, this typically means US operating subsidiaries. Check the regulation's definition of "doing business in California" with counsel rather than relying on sales figures alone.

What does the first SB 253 report need to contain?

Scope 1 and Scope 2 emissions for the first reporting year. Companies can submit through CARB's voluntary online intake platform or by email.

• Scope 1 and 2 emissions. First filing (due 10 November 2026): Required; 2027 and later: Required annually.
• Scope 3 emissions. First filing (due 10 November 2026): Not required; 2027 and later: Begins in 2027, details in a separate CARB rulemaking.
• Third-party assurance. First filing (due 10 November 2026): CARB will accept submissions regardless of whether limited assurance was obtained; 2027 and later: To be set in the separate rulemaking.
• Companies not collecting data as of 5 December 2024. First filing (due 10 November 2026): Statement of non-reporting to obtain first-year relief; 2027 and later: Full reporting expected.
• Methodology. First filing (due 10 November 2026): GHG Protocol standards and guidance; 2027 and later: GHG Protocol, at least through 2033 under the statute.

One nuance on enforcement flexibility: Morgan Lewis notes that it "does not eliminate the reporting obligation," and that companies relying on it should document their good-faith compliance efforts.

What happens to SB 261 climate risk reporting?

It remains on hold. The Ninth Circuit has enjoined enforcement of SB 261 pending appeal, and CARB has said it will not enforce SB 261 while the injunction is in place. The injunction does not extend to SB 253.

In other words: do not let the SB 261 litigation headlines slow down your SB 253 filing.

What should in-scope companies do before 10 November?

Use the remaining weeks for a focused, defensible first filing:

1. Confirm scope. Test each US entity against the revenue threshold and the regulation's definition of doing business in California.
2. Decide: file or non-reporting statement. If the entity was neither collecting nor planning to collect Scope 1 and 2 data as of 5 December 2024, the non-reporting statement route may apply. Document the basis.
3. Lock the inventory boundary. Align organisational and operational boundaries with the GHG Protocol and with what the group reports elsewhere, such as CSRD or CDP.
4. Run a QA pass. Check units, completeness by site and month, and that your Scope 2 method choices are documented before submission.
5. Keep the evidence. Store activity data, emission factors and calculations with an audit trail. Assurance is not required this year, but it is coming.

Need a second pair of eyes on your first filing? Book a free consultation with our carbon accounting team.

Why is 2027 the real challenge?

Because Scope 3 is where most of the data lives outside your company. Scope 1 and 2 come from your own meters and invoices. Scope 3 depends on suppliers, logistics providers and customers, and it is usually the largest share of the footprint: companies disclosing through CDP reported 2023 supply chain emissions averaging 26 times their Scope 1 and 2 emissions (CDP and BCG).

Under the statute as enacted in 2023, the timeline is demanding:

• Scope 3 disclosure starts in 2027.
• Limited assurance on Scope 1 and 2 applies from 2026 and moves to reasonable assurance from 2030; limited assurance on Scope 3 applies from 2030.
• Administrative penalties are capped at USD 500,000 per year.
• Scope 3 misstatements made with a reasonable basis and in good faith are protected by a safe harbor, and between 2027 and 2030 CARB will only penalise Scope 3 for failure to file.

CARB staff have indicated that the separate rulemaking for 2027 onwards will cover Scope 3 and third-party assurance, without a specific date yet. The safe harbor lowers the penalty risk, not the work. Supplier data programs take more than one reporting cycle to mature, which is why the planning needs to start now.

The topic is also moving up event agendas: the Climate Resilience Innovation Forum USA (New York, 2 to 3 December 2026) includes a plenary on how mandatory disclosure is driving climate action "from California to New York" (Innovation Forum agenda).

How does CO2 AI help with SB 253?

Your first SB 253 filing proved you can report Scope 1 and 2. The next test is harder: Scope 3 comes in from 2027, assurance tightens, and the same numbers have to hold up across California, CSRD and CDP. CO2 AI builds one GHG Protocol–aligned inventory across all three scopes, with every figure traceable to its source, so your auditor tests one dataset instead of three. Enterprises like Reckitt, Klöckner & Co and Accor use it to move from compliance to actual reduction.

‍See corporate footprinting → · See compliance workflows →

Frequently asked questions

When is the first SB 253 report due?

The first SB 253 report, covering Scope 1 and Scope 2 emissions, is due on 10 November 2026. California's Office of Administrative Law approved CARB's Initial Regulation on 12 October 2026, which formally established this deadline. Companies can submit through CARB's online intake platform or by email.

Is assurance required for the 2026 SB 253 filing?

CARB has said it will accept 2026 submissions regardless of whether limited assurance has been obtained. Assurance requirements for 2027 and later years, including for Scope 3, will be addressed in a separate CARB rulemaking. Companies should still keep a full audit trail to prepare for assurance.

When does Scope 3 reporting start under SB 253?

Scope 3 reporting is scheduled to begin in 2027. CARB will set the details, including assurance, in a separate rulemaking. Under the statute, Scope 3 misstatements made in good faith with a reasonable basis are protected by a safe harbor, and penalties until 2030 apply only for failure to file.

Is SB 261 in force?

SB 261 climate-related financial risk reporting is not being enforced. The Ninth Circuit has enjoined its enforcement pending appeal, and CARB has said it will not enforce SB 261 while the injunction remains. The injunction does not apply to SB 253, so emissions reporting obligations continue.