CA SB 253 Implementation: CARB's Workshop Fills in the Details

The California Air Resources Board (CARB) held a public workshop on March 23, 2026, to lay out proposed implementation details for CA SB 253. During the workshop, the CARB staff covered proposed concepts for Scope 1, 2 and 3 greenhouse gas emissions reporting, accounting methodologies and assurance.

Here are the highlights: 

The Basics

For U.S. Companies doing business in California with over $1 billion in annual revenue, the August 10, 2026 reporting deadline remains unchanged. Companies must report their Scope 1 and 2 emissions.

Reporting will follow the company's fiscal year – those with fiscal years ending before February 1, 2026, should report FY25-26 data, while those ending after should report FY24-25 data. Limited assurance is no longer required for 2026 reporting, and companies will not be required to use a standardized template for reporting.

Scope 1 & 2 Reporting

• Standardized Templates: CARB will develop standardized templates for reporting in 2027 and subsequent years. CARB published a draft template for reporting Scope 1 and 2 GHG emissions in October 2025 and is requesting feedback from the public prior to finalization. 

Scope 3 Phase-In

CARB is evaluating and requesting feedback on three primary pathways for Scope 3 reporting in 2027:

• Option 1: Broad Applicability – All reporting entities report on all 15 Scope 3 categories with possible flexibility to exclude categories deemed de minimis (with appropriate explanation)

• Option 2: Sectoral Phase-In – Scope 3 reporting would first be required from transportation and industrial sectors (including technology and energy, cement production, and manufacturing), with the probably phase-in of other sectors in subsequent years. 

• Option 3: Category-based Phase‑In – Companies begin with the five most commonly reported categories – Business Travel (Cat. 6), Purchased Goods and Services (Cat. 1), Fuel and Energy Related Activities (Cat. 3), Employee Commuting (Cat. 7), and Waste Generated in Operations (Cat. 5) – and expand over time

Accounting Methods, Assurance and Cost

• Two options for organizational boundaries. Companies will be able to choose between an equity share approach or a control-based approach (financial or operational), which closely tracks GHG Protocol practice and clarifies how to treat subsidiaries and joint ventures.

• Flexibility in Scope 3 accounting methods. CARB has indicated that spend‑based, activity‑based, supplier‑specific, and hybrid methods will all be acceptable. CARB also clarified that is it not proposing a requirement for companies to collect data directly from suppliers. This is a meaningful relief signal for companies worried about mandatory supply chain data requests. 

• Assurance expectations are crystallizing. Beginning with the 2027 reporting cycle, CARB is proposing limited assurance for Scope 1 and 2. They are proposing the use of multiple assurance standards to reduce friction.

• Near‑term engagement window. There is an active comment period (through mid‑April 2026) specifically on organizational boundaries, accounting methods, emissions factors, and Scope 3 phase‑in design, giving companies a short runway to influence final rules (Comments may be submitted via the public docket established by CARB or by email to ClimateDisclosure@arb.ca.gov).

What Companies Should Focus on Now

• Confirm if you are in scope. Validate whether your U.S. entity exceeds 1 billion dollars in annual revenue and is “doing business” in California; if yes, treat SB 253 as a core compliance program, not a peripheral ESG initiative.

• Get Scope 1 and 2 “report‑ready” by 2026. Submit FY 2025 data by the August 10, 2026 deadline. Plan for internal controls and documentation that will support limited assurance coming in 2027.

• Start mapping Scope 3, even if details aren’t final. Identify your most material categories, where data is already available, and where you may need proxies, so you can adapt quickly regardless of whether CARB adopts the broad, sectoral, or category‑based phase‑in approach.

• Engage in the current comment period. If these topics materially affect your business, coordinate legal, finance, sustainability, and investor relations input and submit feedback while CARB is still in concept‑shaping mode (Comments may be submitted via the public docket established by CARB or by email to ClimateDisclosure@arb.ca.gov).

• Plan for standardized templates and disclosure portals. Expect updated reporting templates for Scope 1 and 2 and more detail on the online reporting portal later this year.

   

The regulatory details are coming into focus — but there's still time to shape them and prepare. If you'd like help assessing your boundary methodology, Scope 3 exposure, or reporting strategy, reach out to our team.

Disclaimer: The information provided does not, and is not intended to, constitute legal advice; instead, all information, content, and materials available are for general informational purposes only.