With the end of the year on the horizon, many companies have started the process of preparing reports for California’s Climate Corporate Data Accountability Act (SB 253). Organizations under the scope of the law will need to disclose their scope 1 and 2 emissions in 2026, using data from 2025. Gathering, calculating, and disclosing this information can seem daunting, especially if it’s your first time. Below, we share a simple checklist to help get you started.?
What Does SB 253 Require (and When)?
SB 253 requires US companies with over $1B USD in annual revenue doing business in California to disclose their greenhouse gas emissions annually. They must report their scope 1 and 2 data starting in 2026 (with an anticipated deadline of June 30), and their scope 3 data starting in 2027.?
Companies must also seek third-party assurance of their carbon reporting on a phased basis, starting with limited assurance for scopes 1 and 2 in 2026. CARB is considering assurance standards such as ISSA 5000, AA1000, ISO 14060, and AICPA, and will finalize guidance.
Organizations that fail to provide adequate reports will face potential penalties of up to $500,000 per year—though the California Air Resources Board (CARB) has indicated that in the first year of implementation, it will be looking for good faith efforts to comply, not perfection.?
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? Want to go deeper? Watch our on-demand California Climate Updates webinar for expert guidance on SB 253 and related disclosure laws.
Preparing Your First SB 253 Report: A Checklist
Gathering and calculating emissions data can be complex and resource-intensive, especially in the beginning. To streamline the process, we’ve created a checklist. Following the steps below will help you save time and avoid bottlenecks as you prepare your first report.?
1. Make sure you understand SB 253 requirements and deadlines?
This may seem obvious, but it shouldn’t be overlooked. Since SB 253 passed, CARB has provided several public workshops and , clarifying the scope and requirements of the law. You can find the latest updates . Using a carbon accounting platform that aligns directly with SB 253 will also help ensure you’re following the most recent guidance.?
2. Identify data needs and sources
You should start by assessing your current processes and identifying any data gaps. Next, you need to figure out where to source the data within your organization. For example, you may need to contact the facilities team for HVAC records, the procurement team for supplier info, and the finance team for spend data. If you have a solid grasp of your organizational structure to begin with, this process will be much more efficient. To facilitate future reporting, document data owners as you go.?
3. Set up a cross-functional working group
Climate disclosure touches many functions. Establishing a working group early reduces bottlenecks and improves accuracy. Typical roles include:
- Sustainability: Brings subject-matter expertise on emissions calculation and reporting standards.
- Legal & Compliance: Ensures disclosures meet regulatory requirements and minimize liability.
- Finance: Provides spend data, validates accuracy, and links emissions to financial reporting.
- Procurement: Accesses supplier information needed for Scope 3 reporting and future compliance.
- Operations: Supplies activity data such as energy use, facilities, and logistics.
- IT: Supports data systems, integration, and security.
By making each function aware of its role early, you reduce bottlenecks, improve data quality, and build a smoother path to assurance and submission.
4. Establish a centralized data management system
Fragmented spreadsheets or manual processes can increase risk of errors. A central repository is a key step for avoiding miscalculations and organizing information from multiple sources. Automated carbon accounting software is the best way to manage data, create scalable frameworks and processes, and prepare for assurance. By leveraging a platform designed specifically for SB 253, you can save considerable time and ensure that your report is aligned with the latest requirements.?
5. Gather data and calculate your carbon footprint?
Collecting data is often the most time-consuming step in the reporting process. You can follow our guidance here to avoid common obstacles.? As you calculate your emissions, you should document your estimation methodologies, emissions factors, operational boundaries, and other assumptions used in the process. Software that automatically generates an SB 253 report will ensure your data is reliable and auditable.?
6. Engage an assurance provider?
You’ll have to find a qualified third-party assurance provider who meets CARB’s criteria for experience and independence. Starting early can help avoid a last-minute scramble (and premium pricing). If you’ve documented your data collection and calculation methods from the beginning, you’ll prevent unnecessary back-and-forth with the provider.?
7. Submit your report?
Once your report has undergone assurance, it’s ready to submit. CARB is developing a digital platform to receive reports, and plans to promote transparency by establishing a public docket for these reports.?
8. Assess your processes?
Data complexity will likely increase in future years, especially as scope 3 requirements phase in. After you submit your first SB 253 report, it’s a good time to review your data collection and management systems and solve any bottlenecks so you can ensure smooth reporting in years to come.?
Looking Ahead?
Your first SB 253 report is an opportunity to set up systems that will support future reporting—not just for California, but for other climate disclosure frameworks like CDP. It’s also a chance to uncover operational efficiencies and cost savings. By aligning the reporting process with your long-term business goals, you’ll be better equipped to adapt to an evolving regulatory and market landscape, turning compliance into a competitive advantage and building lasting business value.
