California’s first corporate emissions reports are due on November 10, 2026, and that date is now final. On October 12, the state’s Office of Administrative Law approved the Air Resources Board’s regulation implementing SB 253, closing the last procedural step between the law and the companies it covers. Four days earlier and three time zones away, the U.S. EPA published a rule moving the federal greenhouse gas reporting deadline for the same emissions era out of 2026 entirely, to March 10, 2027. A company with obligations in both systems now plans to two calendars moving in opposite directions.
What California just locked in
SB 253, the Climate Corporate Data Accountability Act, requires U.S. companies doing business in California with more than $1 billion in annual revenue to disclose their greenhouse gas emissions to the California Air Resources Board (CARB). The first reports cover Scope 1 and Scope 2 emissions — direct emissions and purchased energy — and they are due November 10, 2026. CARB’s preliminary list identified more than 4,000 U.S. companies likely in scope, and the regulator has sent reminder letters to companies it believes are covered.
The November date is itself a moved deadline, which is worth understanding before treating it as permanent. Initial reporting was first set for August 10, 2026. CARB withdrew its regulation from review in June to make limited changes and resubmitted it, pushing the first deadline to November. The difference this time is procedural posture: the regulation has now been approved and is in effect, the reporting guidance and intake platform are published, and the fee schedule starts December 10, when CARB begins issuing annual fee determination notices, payable within 60 days. A deadline with a fee notice attached behaves differently from a deadline in a draft rule.
A firm date with a soft first-year bar
The deadline is hard. The data standard for the first cycle is deliberately forgiving, and the regulation says so in three distinct ways. A reporting company can satisfy November 10 with a Scope 1 and 2 report for its applicable preceding fiscal year. It can instead submit emissions data drawn from information it already had, or was collecting, on or before December 5, 2024 — CARB’s enforcement-notice baseline. Or, if it held no such data and was not collecting it by that date, it can file a statement on company letterhead saying exactly that. First-cycle reports are accepted without limited assurance, and CARB has said it will exercise enforcement discretion for this inaugural cycle.
That structure is a design choice, not a loophole. California is buying a complete census of who reports before it buys precision in what they report. Assurance tightens on a published schedule: limited assurance over Scope 1 and 2 begins with the 2027 cycle, Scope 3 value-chain reporting also begins in 2027, and reasonable assurance arrives in 2030. A company that treats the soft first year as a reason to wait is misreading the sequence — the 2026 filing is the baseline the assured filings will be compared against.
One sibling law needs separating from this deadline. SB 261, which requires companies over $500 million in revenue to publish climate-related financial risk reports, is under a Ninth Circuit injunction pausing its implementation while an appeal runs. The same court declined to halt SB 253. The November 10 emissions deadline is not paused, and a risk-report delay is not an emissions-report delay.
The federal side: one reporting year, three dates
The federal Greenhouse Gas Reporting Program collects emissions data from roughly 8,200 facilities, fuel and industrial-gas suppliers, and carbon dioxide injection sites under 40 CFR Part 98. Its reporting-year 2025 reports were originally due March 31, 2026. A February 2026 rule moved that to October 30, 2026. On October 14, 2026, EPA published an interim final rule, effective immediately, moving it again — to March 10, 2027. One reporting year has now carried three deadlines, each announced as the program’s future was being reconsidered. We covered the federal move and what to do with the extra time in full: EPA Moved the 2025 GHG Reporting Deadline to March 10, 2027.
The reason for the slide is stated in the rule itself. EPA is deciding what to do with its September 2025 reconsideration proposal, which would rework reporting requirements for nearly every source category in the program and suspend the remaining natural-gas-segment obligations until 2034. The agency says it needs the time, and that its reporting system would not have been ready for the October date. The extension changes only the deadline: reporting-year 2025 reports remain owed, and comments on the interim rule are open until November 30, 2026.
Two systems, two populations, one planning problem
These two deadlines are often described as substitutes. They are not. The federal program is facility-level: a plant reports its own emissions because it crosses a source threshold. California’s SB 253 is company-level: an enterprise reports its Scope 1 and 2 footprint because its revenue and its California business cross a statutory line. A manufacturer can owe EPA a facility report in March 2027, owe CARB a corporate report this November, both, or neither — and the data systems behind the two filings overlap without being identical.
The practical reading for compliance teams is sequencing. California’s calendar is the one now in force, with a named date, an open intake platform, and fees that start in December; it sets the working timeline for corporate disclosure regardless of what Washington decides. The federal timeline is genuinely uncertain, but uncertain is not cancelled — records that support a reporting-year 2025 facility filing still need to exist in March 2027 unless the reconsideration removes the obligation outright. And the assurance runway California published — limited assurance in 2027, reasonable assurance in 2030 — means the emissions inventory a company files this November, under good-faith flexibility, becomes the foundation its auditors test later. The state held its date and eased its standard. The federal government eased its date and left its question open. Companies reporting into both should build to the calendar that is actually running.