SB253 Compliance Timeline: What to Do Before November 10, 2026
The order these steps happen in matters more than exactly how many weeks you have left. A phase-by-phase sequence for getting ready.
This is less about a specific calendar date and more about sequencing. The order these steps need to happen in matters more than exactly how many weeks you have left, though how much time you have does change how much you can afford to get wrong along the way.
Phase 1: Foundation
Before anything else, confirm you're actually covered: the revenue threshold and California nexus, checked against your current structure, not an assumption carried over from a general sense of "we're a big company." Then make the organizational boundary decision: operational control, financial control, or equity share. This has to come first because it determines which facilities, vehicles, and leased spaces are yours to report at all. Skipping this step or deciding it implicitly is the single most common reason inventories have to be redone.
Phase 2: Data collection
This is where most of the actual time goes. Pull fuel purchase records for both stationary combustion (boilers, furnaces, generators) and mobile combustion (fleet vehicles, off-road equipment): actual records, not estimates. Pull refrigerant purchase and recharge data for the reporting period specifically, not total system capacity. Pull electricity usage data by facility, and confirm you're set up to calculate both required Scope 2 methods, not just one. If any facility receives purchased steam, heat, or cooling, gather that documentation too. None of this needs to happen in a specific order internally, but all of it needs to happen before you move to calculation. Trying to calculate with partial data means redoing work later.
Phase 3: Calculation and documentation
Apply emission factors with their source and vintage recorded, not just the resulting number. Document your methodology per category as you go, while you still remember the judgment calls you made, rather than trying to reconstruct them afterward. Anywhere you had to estimate instead of using actual data, flag it explicitly and note how the estimate was made. This phase is where an inventory becomes auditable rather than just complete. The numbers and the explanation of the numbers are not the same deliverable.
Phase 4: Review before it goes anywhere
Have someone other than the person who built it look it over. Obvious inconsistencies (a facility with zero recorded electricity use, a fuel total wildly different from expectations) are much easier for a second set of eyes to catch. Specifically check that the boundary decision from Phase 1 was actually applied consistently everywhere, since that's the kind of thing that drifts silently across a multi-week build. Confirm both Scope 2 methods are present and documented, not just one.
If you're short on time
If you're reading this with less runway than you'd like, the priority order doesn't change, but what you can afford to skip does. Real, sourced data on a narrower set of categories beats a comprehensive inventory built on guesses. An auditor can work with "we have solid data on three categories and a documented, honest gap on a fourth" far more easily than with numbers that look complete but can't be traced back to anything. If the boundary questions or the volume of judgment calls are genuinely beyond what you can resolve confidently in the time left, that's the moment to seriously weigh bringing in outside help rather than pushing through alone.
Phase 1 and 2 are exactly what the Scope 1 & 2 Data Collection Checklist is built around. If you haven't started, that's the place to begin.