CARB has pushed the first SB 253 reporting deadline from August 10 to November 10, 2026, after withdrawing its initial regulation to clarify requirements. The delay bought time but didn’t remove the obligation. For covered businesses, the first real compliance cycle is now underway.
The immediate focus is Scope 1 and Scope 2, with the first report due November 10, 2026.
Scope 3 comes later, with reporting requirements beginning in 2027.
But there is an important distinction here – “Scope 3 may wait until 2027, but the groundwork for it cannot.”
Companies that build a reliable emissions reporting process now will be ready when the requirements expand, instead of scrambling to adapt at the last minute.
So, what exactly is due first? What can wait? And what should companies be doing now to avoid starting from scratch next year?
Let’s untangle that.
Why SB 253 Matters Now
California’s Climate Corporate Data Accountability Act, or SB 253, was signed into law in 2023 alongside SB 261 as part of California’s broader climate regulation framework.
The goal is straightforward: make corporate greenhouse gas emissions information more transparent and consistent, so investors, customers, regulators and other stakeholders can better understand a company’s emissions.
SB 253 covers U.S. companies doing business in California with over $1 billion in total global revenue, not just California revenue, even if they’re headquartered elsewhere.
First Scope 1 and 2 disclosures, covering fiscal year 2025 emissions, are due November 10, 2026.
Scope 1, Scope 2, Scope 3: What Comes When?
At a high level, the timeline looks like this:
2026 → Scope 1 + Scope 2
2027 onward → Scope 3 + stronger assurance requirements
The three scopes cover different parts of a company’s emissions footprint:
- Scope 1: Direct emissions from sources a company owns or controls, such as fuel combustion.
- Scope 2: Indirect emissions from purchased energy, such as electricity, steam, heating or cooling.
- Scope 3: Other indirect emissions across the value chain, including purchased goods and services, business travel, employee commuting and waste.
The immediate requirements for the first reporting cycle are Scope 1 and Scope 2.
Why Scope 1 and 2 Are More Complicated Than They Look
On paper, Scope 1 and Scope 2 reporting sounds simple:
Collect the data → calculate emissions → report the numbers.
In practice, it rarely works that neatly.
Large organisations can have multiple entities, facilities and operations spread across different locations. Energy and fuel data may sit in utility bills, ERP systems, facility records, fleet systems, procurement platforms or existing emissions inventories.
And once the number is calculated, more questions follow:
- Where did the activity data come from?
- Which emission factor was used?
- Why were those methodologies chosen?
- What assumptions were made?
- Can someone trace the final emissions figure back to the original evidence?
Now, the question changed from “What are our emissions?” to “Can we explain where that number came from?” This shift from calculating emissions to being able to explain and substantiate them is central to the reporting process.
The 2026 “Good Faith” Window Is Not a Free Pass
The first reporting year comes with some flexibility.
For the 2026 reporting cycle, CARB has emphasized good-faith efforts toward compliance, particularly for companies working through their first reporting process.
Good faith simply means making reasonable efforts to establish the reporting process, collect available data, identify gaps and work toward addressing them. It does not mean submitting a number simply because a deadline is approaching.
What a strong good-faith process looks like:
- A clearly defined reporting boundary
- Reliable available data
- A documented methodology
- Traceable calculations
- Supporting evidence
- Clear ownership
- Review and control processes
The goal is to be able to show how you got to the number.
You May Not Need to Build a New CARB Report from Scratch
CARB’s current guidance and voluntary intake process allow companies to use existing Scope 1 and Scope 2 information rather than starting with a completely new reporting process.
Companies preparing to report may already have work they can build on. Existing disclosures such as CDP, CSRD, ISSB, or BRSR can provide a starting point, so there is no need to build a separate process from scratch.
The focus now should be on making that information consistent, defensible, and traceable.
What Waits Until 2027?
This is where Scope 3 comes in.
Scope 3 reporting will follow the first Scope 1 and Scope 2 reporting cycle, with the detailed 2027 requirements still being worked out by CARB. The current proposal would introduce Scope 3 reporting in phases, instead of asking companies to report all 15 categories at once.
The categories initially proposed for reporting are:
- Purchased goods and services
- Fuel- and energy-related activities
- Waste generated in operations
- Business travel
- Employee commuting
Scope 3 reaches far beyond a company’s own operations
Research from Boston Consulting Group found that companies’ reported supply-chain Scope 3 emissions were, on average – 26 times higher than their operational Scope 1 and Scope 2 emissions.
That puts the scale of the challenge into perspective.
2027 Also Changes the Assurance Equation
There is another reason companies should look beyond the November deadline.
For the 2026 cycle, limited assurance for Scope 1 and Scope 2 is not required under CARB’s first-year approach. However, from 2027, CARB’s proposed framework would introduce limited assurance for Scope 1 and Scope 2 emissions.
That means companies will need more than accurate numbers. They will need a clear trail showing where the data came from, how it was calculated, and what supports it.
A useful way to think about the process is:
Source data → Calculation → Emission factor → Emissions figure → Evidence → Review
That chain should be built into the reporting process now, rather than added when assurance requirements become more demanding.
What About SB 261 and the SB 253 Lawsuit?
It is easy to group California’s climate disclosure laws together, but SB 253 and SB 261 address different reporting requirements.
SB 253 focuses on corporate greenhouse gas emissions reporting, including Scope 1, Scope 2 and, eventually, Scope 3.
SB 261, meanwhile, focuses on climate-related financial risk reporting.
There is also ongoing litigation surrounding California’s climate disclosure laws. The legal situation has affected SB 261 enforcement, while SB 253 implementation continues as CARB moves forward with its reporting program.
For companies preparing for SB 253, the important point is that the regulatory process is continuing, with November 10, 2026, remaining the key first reporting deadline.
That means companies should keep monitoring developments but should also keep moving their reporting work forward.
The Real Deadline Is Bigger Than November 10
November 10 is the immediate deadline, but it should not be the finish line.
If reporting still depends on chasing invoices, reconciling spreadsheets, and rebuilding calculations, the same challenges will return next year, with more data, Scope 3, and assurance requirements.
The goal now is simple: build a process you can repeat, not one you must rebuild.
So, what should companies do now?
- Confirm the reporting boundary: Know which entities, facilities and operations are included.
- Map the data: Identify where Scope 1 and Scope 2 information lives across energy, fuel, facilities, fleet, procurement and ERP systems.
- Document the methodology: Record emission factors, units, calculations and assumptions.
- Build traceability: Make sure every reported figure can be connected to its supporting evidence.
- Add controls: Establish validation, review, approval and version-control processes.
- Track data gaps: Document what is missing instead of leaving gaps unexplained.
- Start looking at Scope 3: Identify relevant categories, suppliers and data sources that will matter in 2027.
The aim is to make the next reporting cycle easier than the first.
Scope 1 and Scope 2 are due first. Scope 3 comes next. Get the first filing right and build a process that makes the next one easier.
