California SB 253 · Limited assurance begins with 2027 reports

Assurance-ready emissions inventories
for California's SB 253.

Reports filed in 2027 must include limited assurance of Scope 1 and 2 emissions. For a calendar-year company, the FY2026 records an assurance provider will test are being created now. Koru prepares the inventory they review.

Check if SB 253 applies to you See what we do
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The Reality

The first filing was the easy part.
Assurance is next.

SB 253 applies to US companies with more than $1 billion in annual revenue that do business in California. Many privately held companies in scope have no sustainability team, so the obligation lands with the controller or CFO.

01

You may already be in scope

SB 253 applies above $1 billion in revenue, measured as the lesser of your last two fiscal years, not just the current one. California's own outreach to qualifying companies has been unreliable, so many affected companies don't yet know they're covered.

02

Limited assurance starts with FY2026

Reports filed in 2027 cover FY2026 and must include limited assurance of Scope 1 and 2 emissions by an independent provider. The hard part is rarely the math: it is finding the data across utility bills, fuel cards, and service logs, and documenting each number so an assurance provider can trace it to its source.

03

Scope 3 is coming, without assurance

CARB has proposed adding five Scope 3 categories in 2027, without assurance. The list is not final yet, so start with screening estimates and a documented relevance decision for the other ten categories.

What Koru Does

Built for California climate disclosure — not generic ESG.

Koru pairs hands-on consulting with a purpose-built software platform, because compliance-grade emissions data still takes real work, no matter how good the tool is.

Applicability & Gap Review

Confirm whether and when SB 253 applies, using the statutory revenue threshold and California nexus tests. Then check your filing or current records against what a limited-assurance provider will test.

GHG Inventory

A GHG Protocol-aligned Scope 1 and 2 inventory, with every number traced to its source document, emission factor, and method — built so it can be assured and restated. Screening estimates for CARB's five proposed Scope 3 categories are available as an add-on.

Assurance Evidence

An evidence binder of source documents and calculations, indexed the way assurance providers request them, and a mock assurance walkthrough of the checks your provider will run, done first.

Ongoing Reporting Infrastructure

A client portal that keeps your inventory organized year over year, so next year's disclosure doesn't depend on one person's memory of how last year's numbers were built.

Engagements

Two ways to work with Koru

Start here · about 2 weeks

Assurance Gap Review

A review of your 2025 filing or current records against what a limited-assurance provider will test.

  • Boundary and source check: which entities, facilities, and emission sources are in, and whether anything is missing
  • Evidence test: a sample of reported numbers traced back to source documents
  • Gap list: issues ranked by what an assurance provider would flag first, with a plan to close each one
Fixed fee · credited toward the Readiness Engagement
6–8 weeks · an assurance-ready FY2026 inventory

Readiness Engagement

Everything an assurance provider will ask for, built before they ask.

  • Data inventory and ownership map: every source, where it lives, who collects it, and who fixes it when it is wrong
  • Scope 1 and 2 inventory with every number traceable to its source document
  • Assurance evidence binder, indexed the way assurance providers request it
  • Mock assurance walkthrough: the inquiries and analytical checks your provider will run, done first
  • CFO summary: your largest sources, year-over-year changes explained, and where emissions and costs overlap
  • Process runbook written to survive staff turnover, plus a post-filing review and next-cycle check-in
Fixed fee, agreed before work starts
Scope 3 add-on: screening estimates for CARB's five proposed categories (purchased goods and services, fuel and energy-related activities, waste, business travel, and employee commuting), with a documented relevance decision for the other ten. Runs alongside the Readiness Engagement.

All work is fixed-fee, scoped to your sites and agreed before it starts; pricing is shared on a first call. Koru prepares and advises. It does not provide assurance or attest services and is not a CPA firm. Your company submits its own filing to the California Air Resources Board and remains responsible for the accuracy of its data. Climate-risk reporting under SB 261 is out of scope.

Book a free 30-minute call
How It Works

From your records to an assurance-ready inventory in three steps.

Koru starts with your actual regulatory exposure — not assumptions. Every engagement begins with your company's specific thresholds, data, and deadline.

1
Check Your Exposure

Answer a couple of questions about revenue and California nexus to see whether SB 253 likely applies to you, and when.

2
Find the Gaps

An Assurance Gap Review checks your filing or current records against what a limited-assurance provider will test, and ranks what to fix first.

3
Build It Assurance-Ready

A Readiness Engagement builds your FY2026 Scope 1 and 2 inventory, evidence binder, and runbook, so assurance and next year's filing don't start from scratch.

Check Your Exposure

Does SB 253 apply to you?

Answer two quick questions using your own numbers. This is a general guide, not legal advice — Koru can help you confirm your exact status.

Answer both questions above to see your likely status.
Talk to us about your specific situation
About
Alex Istock
Founder, Koru Reporting

Alex Istock is an accounting and sustainability consultant with hands-on experience advising small businesses through the Detroit Neighborhood Entrepreneurs Project. A future CPA completing a BBA at the University of Michigan's Ross School of Business, Alex brings a practical, systems-oriented approach to helping organizations measure, understand, and communicate performance. Outside of Koru, Alex competes for the University of Michigan men's gymnastics team, the 2025 NCAA national champions.

Koru was founded on the belief that climate disclosure isn't a technology problem — software alone doesn't remove the manual work of building an assurance-ready inventory. The goal is to pair the right tools with the hands-on work SB 253 actually requires, so companies aren't caught unprepared. Koru's approach draws on more than 30 conversations with sustainability practitioners, assurance providers, and finance leaders about where emissions reporting breaks down.

Accounting Consultant — Detroit Neighborhood Entrepreneurs Project
BBA, Ross School of Business, University of Michigan
CPA track, minor in Sustainability
Alex Istock