[Updated] California’s First Climate Disclosure Deadline Is Set. But the Bigger Story Still Isn’t the Deadline.
For the past several years, California’s climate disclosure laws have been viewed primarily through the lens of regulatory uncertainty. Companies watched legal challenges unfold, waited for implementing regulations, and tried to determine whether reporting deadlines would shift. Much of the conversation centered on when companies would have to report rather than what the legislation was signaling about the future of greenhouse gas information.
That uncertainty has not disappeared, particularly for reporting after 2026. However, the immediate path is now considerably clearer.
On September 1, 2026, the California Air Resources Board released guidance for the first reporting cycle under Senate Bill 253, California’s Climate Corporate Data Accountability Act. Covered companies are expected to submit their Scope 1 and Scope 2 greenhouse gas emissions by November 10, 2026. CARB also introduced a voluntary intake platform and clarified what companies can submit, how first-year assurance will be treated, and which emissions factors may be used.
The first deadline now has a practical reporting process. But the larger lesson remains the same: California’s requirements are one part of a much broader shift that is making credible greenhouse gas information part of normal business infrastructure.
What Companies Need to Submit in 2026
SB 253 generally applies to companies formed under U.S. law that do business in California and have more than $1 billion in annual revenue. Those companies will ultimately be required to report Scope 1, Scope 2, and Scope 3 emissions, although only Scope 1 and Scope 2 are included in the 2026 reporting cycle.
CARB’s September 1 reporting guidance gives companies several options for meeting the first deadline. A covered company may submit an existing annual report containing its Scope 1 and Scope 2 emissions, information previously reported through another regulatory or voluntary program, or data prepared using CARB’s draft reporting template.
This means the first California filing does not necessarily require a separate report or an entirely new greenhouse gas inventory. If a company already has credible Scope 1 and Scope 2 data, the immediate challenge may be determining whether that information is complete, appropriately documented, and suitable for public submission.
CARB has also launched a voluntary intake platform through which companies can submit reports, provide contact and billing information, or explain that they do not plan to report emissions data in 2026 under CARB’s first-year enforcement approach. Use of the platform is not mandatory. Companies may instead submit their information by email.
The platform permits a single submission on behalf of multiple reporting entities, such as a global-level report covering qualifying subsidiaries within the same corporate group. Companies can also indicate whether the related fees should be invoiced together or separately. CARB expects to issue invoices by December 10, with payment due within 60 calendar days of the invoice date.
Companies should recognize that the submission is not simply an administrative exchange with CARB. Emissions reports and statements of non-reporting uploaded through the platform will be made public. That makes consistency with sustainability reports, CDP responses, financial disclosures, customer questionnaires, and other external communications particularly important.
CARB Is Providing First-Year Flexibility
CARB is exercising enforcement discretion for the first reporting cycle. Although SB 253 calls for limited assurance beginning in 2026, CARB will accept submissions whether or not assurance has been obtained.
Companies that were neither collecting nor planning to collect Scope 1 and Scope 2 information as of December 5, 2024, are not expected to create historical emissions data solely for the first reporting cycle. CARB instead recommends submitting a signed statement on company letterhead explaining that the company was not collecting or planning to collect the information at that time.
This is a meaningful accommodation, but it should not be interpreted as a general exemption from future reporting. CARB explicitly states that the guidance and related enforcement discretion apply only to the 2026 reporting cycle.
A company that submits a non-reporting statement this year should still begin establishing the systems it will need for future reporting. The statement addresses a specific historical circumstance. It does not eliminate the underlying reporting obligation or the need to prepare for the requirements that will follow.
Flexible Reporting Does Not Mean the Methodology No Longer Matters
For 2026, CARB primarily requires reporting companies to provide annual Scope 1 and Scope 2 totals. It also encourages them to include supporting information where available, including organizational boundaries, methodologies, data sources, emissions factors, global warming potential values, assumptions, and emissions disaggregated by source or greenhouse gas.
Those details may not all be mandatory during the first cycle, but they are what transform an emissions number into a defensible public disclosure.
Two companies can report the same emissions total while using different organizational boundaries, factor sources, estimation methods, or approaches to purchased electricity. Without the accompanying context, it can be difficult to determine whether the results are complete, comparable, or appropriate for future assurance.
CARB has provided additional flexibility because EPA’s 2024 Emissions & Generation Resource Integrated Database, commonly known as eGRID, was not released on its customary schedule. Companies may use the latest official EPA dataset, eGRID 2023, the independently generated eGRID 2024 dataset identified by CARB, or another credible emissions-factor source. Companies are encouraged to identify the factors they used and where those factors came from.
The practical takeaway is that first-year flexibility should reduce unnecessary rework, not lower the standard for documentation. A company may be able to submit an existing inventory, but it should still understand how that inventory was constructed and whether the same methodology can withstand public scrutiny and future assurance.
The 2026 Filing Is a Starting Point, Not the Long-Term Model
CARB is developing a separate regulation for reporting in 2027 and beyond. That rulemaking will address accounting methodologies, reporting formats, deadlines, assurance requirements, and Scope 3 emissions.
Until those requirements are finalized, companies should avoid assuming that the flexibility available in 2026 will continue unchanged. An existing sustainability report may be sufficient for the first filing, but future reporting will likely require stronger controls, more consistent methods, and a clearer assurance trail.
That makes the first submission more than a compliance deadline. It is an opportunity to test whether a company’s emissions system can support what comes next.
Can the organization explain its reporting boundary? Are emissions factors and calculation files documented? Can facility data be traced back to invoices, meters, fuel records, or other source documents? Are responsibilities divided clearly across sustainability, finance, operations, EHS, and procurement? Could an independent reviewer reproduce the results?
The answers matter well beyond California.
Most Suppliers Will Feel the Effects Without Filing a Report
For companies below California’s $1 billion revenue threshold, it may be tempting to conclude that SB 253 is someone else’s reporting problem. In practice, the distinction between a regulated company and its suppliers is less protective than it first appears.
Scope 3 emissions cannot be calculated without information about the value chain. Beginning in 2027, larger companies reporting under SB 253 will need to address emissions associated with purchased materials, transportation, business travel, waste, product use, and other upstream and downstream activities.
For specialty chemical manufacturers, ingredient producers, CDMOs, laboratories, packaging companies, and other upstream suppliers, the reporting obligation may therefore arrive through a customer rather than a regulator.
The exact form of those requests is not yet settled. CARB is still developing the post-2026 Scope 3 methodology, and companies should be careful not to present speculative requirements as final. What is clear is that large customers increasingly need better information about the emissions embedded in the products and services they purchase.
California is reinforcing a pattern already visible through CDP, EcoVadis, SBTi supplier-engagement targets, product carbon footprints, customer questionnaires, and global reporting standards. Information that once remained inside operational systems is moving across organizational boundaries.
For many mid-market suppliers, that commercial shift will be more consequential than the regulation itself.
Reporting Has Become a Data-Management Challenge
Organizations often assume that the difficult part of sustainability reporting is preparing the final disclosure. In reality, the disclosure is simply the visible output of a much larger system.
Before a credible report can be published, companies must establish organizational boundaries, collect facility and activity data, identify appropriate emissions factors, document calculation methods, define responsibilities, and prepare the information for review. Those processes require coordination across functions and cannot be assembled reliably a few weeks before a deadline.
The same underlying system can also support customer questionnaires, product carbon footprints, science-based targets, CDP responses, EcoVadis assessments, sustainability reports, and other emerging disclosure requirements.
The inventory becomes an organizational asset rather than a single-purpose compliance product.
The Most Efficient Companies Will Build Once and Use the Data Many Times
One of the most persistent misconceptions surrounding sustainability regulation is that each framework requires an entirely separate reporting process. California, CSRD, ISSB, GRI, CDP, EcoVadis, SBTi, product carbon accounting, and customer requests are often treated as independent projects, each accompanied by a new spreadsheet and a new data-collection exercise.
In practice, these frameworks overlap far more than they differ.
They rely on many of the same activity data, calculation methods, governance structures, and documentation controls. Organizations that build those capabilities once can use them across multiple requirements. Those that approach every request independently repeatedly collect the same information, increase costs, and create a greater risk that different disclosures will tell different stories.
California’s first reporting cycle reflects that logic. CARB is allowing companies to use credible information they already possess instead of requiring every organization to rebuild its inventory around a new template.
The immediate question for a covered company is therefore not simply, “What document should we submit by November 10?” It is, “Do we have a sufficiently credible emissions system to support this public submission and the requirements that will follow?”
For suppliers and mid-market businesses outside the direct reporting threshold, the question is similar. Is the organization building the information customers will increasingly expect, or will each new request trigger another improvised response?
The deadline matters. But the system behind the disclosure will determine whether reporting remains a recurring burden or becomes a capability the business can use.