California’s Climate Corporate Data Accountability Act Deadlines

California has a reputation for setting the pace on climate policy. With the Climate Corporate Data Accountability Act
(commonly referred to as SB 253), it’s now trying to set the pace on corporate emissions transparency too. If your
company does business in California and clears the revenue threshold, the question is no longer “Should we track
emissions?”it’s “Can we do it on time, with enough confidence to put it on the internet without breaking into a cold
sweat?”

This guide walks through SB 253’s key deadlines (what’s locked into statute versus what California Air Resources Board
(CARB) is still finalizing), how the timeline interacts with assurance requirements, and the practical “what do we do
next?” steps that separate calm compliance teams from those living on espresso and hope.

What SB 253 requires (in plain English, with minimal legal throat-clearing)

SB 253 requires certain large, U.S.-based business entities that do business in California and have
more than $1 billion in annual revenue (based on the prior fiscal year) to publicly disclose
greenhouse gas (GHG) emissions across:

• Scope 1: Direct emissions from sources the company owns or controls (think fuel burned in company facilities or fleet vehicles).
• Scope 2: Indirect emissions from purchased electricity, steam, heating, or cooling.
• Scope 3: Other indirect emissions up and down the value chain (purchased goods and services, business travel, employee commuting, product use, and more).

SB 253 also points companies to the Greenhouse Gas Protocol as the measurement foundation, and it
contemplates third-party assurance (more on that timeline in a bit). Reporting can be consolidated at the parent level,
which is helpfulbecause the alternative is every qualifying subsidiary reinventing the same spreadsheet in parallel.

The deadline map: what’s fixed vs. what CARB is still setting

SB 253 includes “start years” in statute, but it also instructs CARB to develop regulations that establish key details
like the specific reporting dates and mechanics. In other words: the law gives you the calendar year; CARB
fills in the day and time.

High-level statutory timeline (the big rocks)

• By July 1, 2025: CARB is directed to adopt regulations implementing the reporting program (this deadline was established in the amended statutory language).
• Starting in 2026: Scope 1 and Scope 2 disclosures begin, on or by a date to be determined by CARB, and annually thereafter.
• Starting in 2027: Scope 3 disclosures begin on a schedule specified by CARB, and annually thereafter.
• 2029–2030: CARB must review and potentially update disclosure deadlines to bring Scope 3 reporting as close in time as practicable to Scope 1 and 2, and update assurance/provider qualification expectations as required.
• 2033+: CARB may assess alternative globally recognized standards and (if it switches) adopt new regulations to align the program.

What CARB has proposed so far: a “first-year only” due date

Because SB 253 says “starting in 2026” but didn’t hardcode a specific day, CARB staff has been building an “initial
regulation” package that focuses on two urgent basics: (1) program fees and (2) a first-year-only
reporting deadline for Scope 1 and 2. The proposed first-year due date is:

Proposed first Scope 1 & Scope 2 reporting deadline: August 10, 2026

CARB’s rationale is practical: August 10 aligns with an existing verification deadline under California’s Mandatory
Reporting Regulation (MRR), which could reduce “deadline whiplash” for companies already reporting under other CARB
programs. CARB has also indicated that this first-year report may be based on best-available data.

A timeline you can actually use: Year, data year, and what’s due

SB 253 is structured around reporting your emissions for the prior fiscal year. That sounds simple
until you remember that not all companies have a December 31 year-end and that “prior fiscal year” can mean different
things in year one depending on how the first deadline is set.

CARB’s staff materials describe a proposed first-year approach for the 2026 Scope 1 and 2 submission that accounts for
fiscal-year ends. Under that proposal, companies would generally submit data from the fiscal year ending in 2025, with
an exception for fiscal years ending very early in 2026, and with at least six months after fiscal year end to submit.

Scope 1 & Scope 2 deadlines: what companies should treat as “real” right now

If you only remember three things about Scope 1 and 2 timing, make it these:

1. 2026 is the statutory start year. Waiting for “perfect clarity” is a luxury you don’t havebecause
   emissions programs take time to stand up (systems, governance, internal controls, and yes, convincing people to stop
   emailing spreadsheets with names like “FINAL_v7_REALLYFINAL.xlsx”).
2. CARB has proposed Aug. 10, 2026 for first-year submission. That’s the most concrete date on the board
   right now, and it’s wise to plan around it unless final regulations say otherwise.
3. The first year may allow “best-available data” and good-faith compliance. CARB’s public materials
   signal an intent to support first-year submissions for companies actively working toward compliance rather than
   punishing those still building the plane mid-flight.

Practical example: what the 2026 sprint looks like

Imagine a national retailer with $3.5B in revenue, stores in California, and a fiscal year ending February 2.
Operationally, its Scope 1 data (fleet, generators, refrigerants) lives in facilities and procurement systems, while
Scope 2 data is split between utilities, landlords, and energy suppliers. If the first-year deadline lands in early
August 2026, that company likely needs:

• A complete inventory boundary decision (equity share vs. operational control) aligned with the GHG Protocol.
• A repeatable data pipeline for utility and fuel data, including a method for gaps and estimates.
• Documented calculations and an audit trail that won’t collapse when someone asks, “Where did this number come from?”
• A publication workflow (because the output isn’t just a PDF; it’s a public disclosure with reputational risk).

Scope 3 deadlines: the clock starts in 2027, but the work starts yesterday

Scope 3 is where companies learn humility. It’s value-chain emissionsmeaning a lot of your data depends on other
organizations, other systems, and sometimes other planets (or at least it feels that way).

Statutorily, Scope 3 reporting begins in 2027 for the prior fiscal year, but the exact schedule is to
be specified by CARB regulations. The law also directs CARB to review Scope 3 disclosure timing later in the decade to
bring it as close as practicable to Scope 1 and 2 timing.

The good-faith “safety features” in the law

SB 253 recognizes that Scope 3 is hard and builds in important guardrails:

• Good-faith misstatement protection: A company is not subject to administrative penalties for Scope 3
  misstatements if it had a reasonable basis and disclosed in good faith.
• Penalty limitation for early Scope 3 years: Between 2027 and 2030, penalties assessed on Scope 3
  reporting are limited to nonfiling.

Translation: California still expects you to file, but it is signaling it won’t treat early Scope 3 as a “gotcha”
contest where honest estimation errors are punished like fraud.

Assurance deadlines: the part everyone circles in red ink

SB 253 contemplates independent third-party assurance as a core feature of the program. The statute provides a phased
approach:

• Scope 1 & Scope 2: Limited assurance beginning in 2026; reasonable assurance beginning in 2030.
• Scope 3: CARB may establish an assurance requirement by January 1, 2027; limited assurance begins in 2030.

At the same time, CARB staff communications around the first reporting year have indicated the agency intends to
exercise enforcement discretion to support good-faith first-year submissionsand that limited assurance is not expected
to be required for 2026 data submission under that first-year approach. The practical takeaway is to plan for assurance
as the end state, but expect the first lap to be more “build the track” than “set the world record.”

Regulatory deadlines and 2025 reality: CARB is building while companies are running

SB 253 directs CARB to develop and adopt regulations by July 1, 2025. As of late 2025, CARB has been moving through a
public workshop process and posting proposed materialsincluding a package aimed at fees and the initial 2026 Scope 1–2
reporting deadline.

Two real-world implications:

• You may not get every implementation detail early. Companies should treat SB 253 as a program to
  build in phasesstarting with core Scope 1 and 2 processes now, and layering Scope 3 complexity next.
• Definitions matter for “are we covered?” decisions. CARB staff has floated definitions for “revenue”
  and “doing business in California” (including ties to existing state tax concepts) for fee and applicability
  purposesso coverage determinations should be revisited as regulations solidify.

Penalties and enforcement: the stick exists, but the law also rewards good faith

SB 253 authorizes CARB to seek administrative penalties for nonfiling, late filing, or other failures to meet the
program requirements. The cap is meaningful:

Up to $500,000 in administrative penalties per reporting year

That said, the statute explicitly directs CARB to consider whether a company took good-faith measures to comply and
when those measures were taken. Practically, that means governance and documentation aren’t “extra”; they’re part of
the compliance story if CARB ever asks what you did to meet the deadlines.

How SB 253 interacts with other climate disclosure pressure (yes, there’s more)

SB 253 is not an only child. California also enacted a climate-related financial risk disclosure law (SB 261) with an
earlier public posting date (January 1, 2026) and a biennial cadence. Litigation has affected SB 261 enforcement timing,
while SB 253 has continued moving forward through CARB implementation work.

The broader lesson: even if you’re only “officially” focused on SB 253, the compliance ecosystem around climate
disclosure is converging. Investors, lenders, customers, insurers, and global counterparties are asking for consistent,
defensible data. Building one strong emissions reporting engine can reduce duplicate work across multiple frameworks.

A no-drama compliance checklist for SB 253 deadlines

Step 1: Confirm whether you’re a “reporting entity” (don’t guess)

• Do you do business in California (based on applicable definitions and emerging regulatory guidance)?
• Did your prior fiscal year revenue exceed $1B?
• Do you have a parent-subsidiary structure where consolidated reporting makes sense?

Step 2: Lock your accounting approach early

• Choose organizational boundaries (operational control, financial control, or equity share) and document the rationale.
• Identify emission sources and map them to data owners (facilities, fleet, procurement, HR, travel, operations).
• Decide what “best-available data” means for you and build an estimation hierarchy.

Step 3: Treat 2026 as a production year, not a pilot

• Create an internal reporting calendar that backs into the proposed Aug. 10, 2026 first-year deadline.
• Build a controls narrative: data collection, review, approvals, change logs, and retention.
• Stress-test the disclosure as if a skeptical reader will fact-check it (because they will).

Step 4: Start Scope 3 now, even if the due date feels far away

• Prioritize the biggest categories (purchased goods, transportation, use of sold products, waste, business travel).
• Begin supplier engagement and contract language updates (data requests become easier when they’re contractually normal).
• Document assumptions and proxiesScope 3 is allowed to use secondary data, but it must be explainable.

Experiences from the real world: what companies learn while racing toward SB 253 deadlines (about )

If SB 253 had a theme song, it would be something upbeat and optimisticplayed over footage of a compliance team
realizing the emissions data is spread across 14 systems, three vendors, and one mysterious folder called “Old Stuff
(Do Not Touch).” The good news is that most companies going through this build-out report the same lessons, and those
lessons are surprisingly practical.

First: the hardest part is not math; it’s ownership. Teams often start with “Sustainability
will handle it,” then quickly discover sustainability needs finance for controls, operations for meters, procurement
for supplier data, HR for commuting assumptions, and legal for what can be said publicly. The companies that move
fastest name an executive sponsor early and treat emissions reporting like financial reporting: clear roles, deadlines,
review layers, and escalation paths.

Second: data quality improves the moment it has a deadline. In early workshops, a lot of teams worry
that their Scope 1 and 2 data isn’t perfect. Then a concrete date appears (like the proposed August 10, 2026), and
“perfect” is politely escorted out of the building. Teams build a repeatable pipeline, identify the biggest gaps,
document estimation methods, and commit to improving year over year. That “continuous improvement” mindset keeps the
first report from becoming a never-ending science project.

Third: Scope 3 is a relationship test. Companies often discover they already have leverageit’s just
not used for emissions data yet. Procurement teams learn to add data-sharing expectations to supplier onboarding, and
category managers learn which suppliers can provide primary data and which will require credible proxies for now. Over
time, this becomes less like pulling teeth and more like standard vendor management, especially when multiple customers
ask for similar information.

Fourth: everybody underestimates “publication work.” SB 253 is about disclosure, not just internal
measurement. That means comms and legal get involved: what context do we provide, what caveats are appropriate, how do
we explain methodology without writing a 90-page novel, and how do we keep messaging consistent with other ESG and risk
statements? Many teams do a “hostile reader review”someone plays the role of critic, looking for confusing language,
missing boundaries, or numbers that don’t reconcile.

Finally: the deadline creates unexpected benefits. Once emissions data is organized, it becomes
usablecompanies identify energy hotspots, fleet opportunities, procurement categories with the biggest footprint, and
operational changes that reduce both emissions and cost. It’s not magic, and it’s not instant, but plenty of teams
report that the reporting engine becomes the foundation for smarter decarbonization decisions. In other words:
compliance may be the reason you started, but operational insight is often why the program sticks.

Conclusion

SB 253’s deadlines are best understood as a phased build: Scope 1 and 2 begin in 2026, Scope 3 follows in 2027, and
assurance expectations tighten as the decade progresses. CARB’s proposed first-year Scope 1–2 due date of August 10,
2026 is the most actionable planning anchor available right now, even as additional regulatory details continue to
develop. The smartest move is to treat emissions reporting like a durable business capabilitygoverned, documented, and
designed to improveso that each deadline becomes a checkpoint, not a panic button.

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