As CARB (California Air Resources Board) continues to develop the detailed requirements for future reporting cycles, companies should use this transition period to build an assurance-ready emissions management process.
This guide breaks down the key steps companies can take to move from “we have calculated our emissions” to “we can defend our emissions data under assurance.”
What You’ll Discover
- CARB’s evolving requirements.
- How to build audit readiness?
- Why does 2026 matter?
- How to prepare for November 10?
- Where can technology help?
Who This Is For
This guide is particularly relevant for:
- Companies subject to SB 253 – Organizations doing business in California that meet the applicable revenue threshold need to prepare for regulated GHG disclosures and assurance requirements.
- Sustainability and ESG teams – Teams responsible for collecting, calculating, consolidating and reporting corporate emissions.
- Finance, risk and internal audit teams – SB 253 brings sustainability reporting closer to the control environment traditionally associated with financial reporting. Finance and assurance functions therefore have an increasingly important role to play.
- Supply chain and procurement teams – Scope 3 reporting depends heavily on data from suppliers and other value-chain partners.
What CARB’s Latest SB 253 Direction Means for Companies
CARB’s ongoing work on SB 253 is giving companies a clearer indication of what future reporting cycles may look like.
While the detailed rules for 2027 and beyond are still being developed, several themes are emerging that organizations should consider when strengthening their GHG reporting processes.
- Closer alignment with the GHG Protocol
- A more defined approach to emissions disclosure
- Greater visibility into data and calculation methods
- More discipline around changes and prior-year data
- Assurance moves from preparation to a mandatory requirement starting in 2027
“2026 is no longer a transition year for SB 253. It is the opportunity to build the data trails, controls and governance that companies will need when mandatory assurance begins in 2027.”
– Christo Philip – ESG Consultant
2026: Use the Grace Period to Build Audit Readiness
The first SB 253 reporting cycle provides companies with some regulatory flexibility. While companies are expected to make a good-faith effort to report their emissions accurately, CARB has indicated that enforcement will be more flexible during the initial reporting year.
This should not be interpreted as a reason for delaying preparation. The 2026 reporting cycle is better viewed as a transition year to identify data gaps, strengthen processes and prepare for mandatory assurance from 2027 onward.
The key question for 2026 is therefore not simply “Can we submit our emissions data?” but “Can we demonstrate that our reporting process is becoming reliable and assurance-ready?”
Key Dates for SB 253
- 2026 – Initial reporting cycle for Scope 1 and Scope 2. Companies should use this period to establish their reporting process, retain evidence and address data gaps.
- 2027 – Scope 3 reporting begins, while limited assurance requirements apply to Scope 1 and Scope 2.
- 2030 – The statutory trajectory moves toward reasonable assurance for Scope 1 and Scope 2, with limited assurance for Scope 3.
Assurance & Verification Requirements
CARB continued to refine its proposed assurance framework for SB 253 reporting, providing additional details regarding both assurance requirements and acceptable assurance standards.
Beginning with FY2027 reporting, CARB is proposing that companies obtain independent third-party limited assurance for Scope 1 and Scope 2 emissions, including separately reported biogenic emissions.
CARB also proposed a list of acceptable assurance standards, including AA1000AS, AICPA AT-C Section 210, ISAE 3410 and ISAE 3000, ISSA 5000, and ISO 14064-3. In addition, the agency is seeking stakeholder feedback on key assurance governance considerations, such as the content of assurance reports, disclosure of other services provided to the reporting entity by assurance providers, and the potential implementation of auditor rotation requirements.
These proposals collectively aim to establish a consistent assurance framework and enhance confidence in reported emissions data.
Choosing the Right Assurance Provider
As SB 253 moves toward mandatory assurance, selecting the right assurance provider will become an important part of the reporting strategy. The right provider should bring more than traditional financial audit experience, they should understand the complexities of GHG accounting, emissions data and sustainability assurance.
When evaluating potential assurance providers, consider the following:
- Choose providers with proven experience in GHG inventory verification and sustainability assurance, not only financial audits.
- Check their experience with relevant standards such as ISAE 3410 and ISO 14064-3, alongside applicable SB 253 requirements.
- Consider providers that can work with digital carbon accounting and ESG platforms to streamline evidence review and data traceability.
Steps to Never Fail your upcoming SB 253 Audit
Passing an SB 253 assurance engagement is not about preparing a perfect emissions inventory at the last minute. It is about building a reporting process where data can be traced, calculations can be explained, evidence can be produced, and controls can be demonstrated.
Use the following five steps to assess where you stand and what needs to happen before your reporting cycle reaches the filing stage.
1- Ready to See Where You Stand?
Taking the readiness test gives you a starting point. The next step is to turn those findings into a clear action plan for November 10.
Use Credibl’s practical checklist to assess whether you have the key building blocks in place for your SB 253 filing from reporting boundaries and GHG methodology to data traceability, evidence, internal controls and final sign-off.
2- Follow Credibl’s Phase-Wise Roadmap to the November 10 SB 253 Submission
Knowing your readiness gaps is only the first step. The next challenge is turning those gaps into a structured plan with clear milestones before the November 10 submission. The roadmap helps your teams understand what needs to happen, when it needs to happen and what “ready” looks like at each stage.
3- Build a foundation for Scope 3
Scope 3 may require a different level of data coordination because much of the information sits outside your direct operational control. Waiting until Scope 3 assurance becomes relevant could leave companies with significant data gaps. The objective isn’t to collect perfect Scope 3 data immediately. It is to create a repeatable process that can progressively move from estimates toward higher-quality, more specific data.
How Credibl Supports your SB 253 Audit Readiness
At Credibl, we help companies shift from spreadsheet-based compliance to audit-grade AI powered carbon intelligence. For firms preparing for SB 253, we offer:
- Automated Workflows, Structured Data Collection
- Smart Collaboration for Internal & External Stakeholders
- Audit & Assurance Readiness
- AI Virtual Auditor module
- AI-powered Data Insights
Top 5 Most Frequently Asked Questions
1. Has the deadline changed?
Yes. CARB moved the Scope 1 and 2 reporting deadline from August 10 to November 10, 2026, and confirmed a phased, five-category approach to Scope 3 starting in 2027. This date is locked in
2. Do we need perfect Scope 3 data before reporting?
No. Scope 3 data can involve estimates, proxies and varying levels of data quality. What matters is that your methodology, assumptions, data sources and limitations are clearly documented and that you have a structured process for improving data quality over time.
3. What evidence should companies retain?
Evidence can include invoices, meter readings, ERP extracts, fuel records, travel records, supplier submissions, calculation files, emission-factor documentation and records supporting data adjustments.
4. What challenges might companies face in complying with SB 253?
Companies might find it challenging to collect all the necessary data, accurately measure Scope 3 emissions, get third-party verification, and fit the new reporting requirements into their existing sustainability plans.
5. What happens if CARB changes the requirements?
This is precisely why companies should avoid building a reporting process around a single regulatory template. A flexible sustainability data architecture allows organizations to update methodologies, reporting structures and disclosure requirements without rebuilding their entire emissions management process.
