In less than a month, your Scope 1 and 2 emissions figure becomes part of the public record with no redaction, confidentiality protections, or opportunity to withdraw it.
Submitting the figure is the easy part. Defending it is harder.
In IRIS CARBON’s recent webinar, The 30-Day Countdown: Getting SB 253-Ready Before November 10, Nabha Rege, Founder of Your Carbon Step, and Farzad Wadia, Director – ESG Solutions at IRIS CARBON, explained what companies should do before the filing window closes and how to prepare for the more demanding years ahead.
SB 253 at a Glance: Who, What, When, and How
California’s Climate Corporate Data Accountability Act (SB 253) is administered and enforced by the California Air Resources Board (CARB). The first-year requirements are:
- Who: US-formed entities doing business in California with total annual revenues above $1 billion.
- What: Scope 1 and 2 emissions calculated in accordance with the GHG Protocol for the fiscal year ending in 2025. Entities whose fiscal year ends between January 1 and February 1, 2026, report fiscal year 2026 instead.
- When: November 10, 2026. The deadline remains subject to final approval by California’s Office of Administrative Law.
- How: CARB’s intake platform and templates are optional in Year 1. Companies may submit by email, through the intake form, or by using existing reports.
CARB has also indicated that it will take a good-faith approach to enforcement in 2026. It will allow flexibility in the form and content of disclosures, and assurance is not required for the first filing.
What Changes After 2026
The flexibility has an expiry date. Under CARB’s proposed rules:
2027
- Scope 1 and 2 require limited assurance.
- Scope 3 phases in with five categories:
-Category 1: Purchased goods and services
-Category 3: Fuel- and energy-related activities
-Category 5: Waste generated in operations
-Category 6: Business travel
-Category 7: Employee commuting
- No assurance is required for Scope 3.
2030: Higher Assurance Expectations
- Scope 1 and 2 move to reasonable assurance.
- Limited assurance for Scope 3 is a possibility.
Nabha pointed out that it’s budget season, so companies should plan for 2027 now. She also advised watching closely for CARB updates as the rules are finalised.
Why Filing Is Easy and Defending Is Not
Once your number is filed, it’s permanent
“There are no redactions, there’s no confidentiality, there’s no takebacks, there’s no unfiling it.”
– Nabha Rege
That number becomes your baseline. Peers, customers, and investors can compare it against others. In 2027, when assurance begins, you’ll also need to show the methodology, emission factor sources, estimates, and assumptions behind it.
Getting Future-Ready: From “What’s Your Number?” to “Can You Prove It?”
Farzad framed the shift simply. This year, the question is what’s your number? Next year, it becomes “Can you prove it?”
That changes the conversation. An external assurer can pick any figure and ask where it came from, who signed it off, why you chose that emission factor, and why it differs from last year.
Most teams can answer these questions. The problem is how long it takes: digging through inboxes, chasing whoever built the spreadsheet, and rebuilding the logic.
Farzad’s readiness test:
“If an assurer asked about any number in the filing for this year, could you answer it in minutes and not weeks?”
Most teams fail this test because they rebuild everything from scratch every year. Farzad noted that before automating, most reporting teams spend roughly 70% of the cycle on manual data work like collecting, chasing, and reconciling inputs, often done by the most expensive people on the team.
The alternative is to build the foundation once and reuse it across CDP, CSRD, CARB, and other frameworks. That foundation has three parts:
- One intake for all your data.
- Versioned methods that record how each calculation was done.
- Evidence attached to every figure.
“The idea here really is to stop treating it as a yearly project and start running it as an ongoing process.” – Farzad Wadia
Expert Tips to Act on Now
- Build control sheets. If you work in Excel, start tracing each figure back to its source today.
- Document data gaps. Note where you relied on spend data instead of activity data, and plan how you’ll improve accuracy.
- Start Scope 3 smart. Check which of the five categories apply to you, then find where the data lives. Category 1 data usually sits in procurement, while commuting data may require employee surveys. Spend-based estimates are a solid start, and you can refine them with supplier-specific data over time.
- Use AI but own the number. As Nabha mentioned: “Remember that it is a tool and remember that you are responsible for the number that you report.” Put the process and ownership in place first and then let tools do the heavy lifting.
How IRIS CARBON Helps: From Priorities to Outcomes on a Single Platform
SB 253 is only one part of the disclosure picture. IRIS CARBON brings strategy, data, calculations, and reporting together in one place.
Double Materiality Assessment: Identify which ESG issues move enterprise value, with board-ready materiality in weeks.
Carbon & Emissions Engine: Get one audit-defensible carbon number across Scopes 1, 2, and 3, and replace months of spreadsheet work with a repeatable process.
ESG Data & Reporting Hub: Collect data once and answer every framework, with fewer errors, faster cycles, and lower assurance costs.
Supply Chain ESG Assessment: Spot supplier ESG risk early, and build Scope 3 from the procurement data you already hold.
Decarbonisation & Net-Zero Roadmap: Prioritise initiatives by ROI and abatement cost and build a net-zero plan your board can defend.
Financed Emissions: See portfolio emissions by asset class, in line with PCAF and regulator expectations. Coverage starts with the steel sector, and we’re adding more sectors over time.
CBAM: Understand your CBAM cost exposure before it hits the P&L, with product-level liability ready for EU declarations.
Climate Risk & Scenario Analysis (coming soon): Quantify climate exposure in financial terms, with TCFD/ISSB disclosure covered.
One intake. Evidence behind every figure. Reports for CARB, CSRD, CDP, and more.
