Scope 3 emissions reporting requirements: which US rules mandate Scope 3 reporting, the revenue thresholds and the 2026 and 2027 deadlines

Last updated September 2026. No US federal rule requires Scope 3 emissions reporting today. The EPA Greenhouse Gas Reporting Program covers direct emitters and fuel suppliers, not value chain emissions. The SEC dropped Scope 3 from its climate rule before adopting it in 2024, that rule was stayed and never applied, and the SEC proposed rescinding it entirely in a notice published June 3, 2026. The one US law that does mandate Scope 3 is California SB 253, which reaches companies with more than $1 billion in total annual revenue that do business in California, and its Scope 3 requirement begins in 2027. The report due November 10, 2026 is Scope 1 and Scope 2 only.

In practice, though, far more US companies are producing a Scope 3 number because a customer, an investor or a ratings program asked for one. Those requests are contractual rather than legal, and they arrive with their own thresholds and their own deadlines. Both kinds of obligation are set out below.

Only under California SB 253, and only from 2027. There is no federal Scope 3 mandate. A US company with under $1 billion in revenue and no California nexus has no legal Scope 3 reporting obligation at all in 2026, which is a materially different position from a company of the same size in the European Union. What that company usually does have is a customer contract or a ratings deadline that asks for the same number.

The EPA line is the one that trips up the most people, because a company can be a mandatory federal greenhouse gas reporter and still have no Scope 3 obligation whatsoever. Coverage under 40 CFR 98.2(a) turns on direct emissions from your own facilities, at a threshold of 25,000 metric tons CO2e combined across applicable source categories, or on the products you supply into the economy. Nothing in the program asks what your suppliers emit. If your compliance calendar has EPA in it, the relevant page is EPA GHG reporting, and the Scope 3 work sits alongside it rather than inside it.

Under SB 253, a company with more than $1 billion in total annual revenue, formed under the laws of any US state or the District of Columbia, that does business in California. Revenue is measured on the whole entity, not on the California portion, so a company with $1.2 billion of national revenue and a modest California presence is in scope while a California-only business at $400 million is not.

The second half of that test is the one that gets read too quickly. Doing business in California is assessed at the individual entity level under Revenue and Taxation Code section 23101(b), not at the group level, and the thresholds are low.

A single remote employee in California, or a distributor relationship worth under a million dollars, can be enough to put an entity over the line. The practical consequence for a large group is that the entity list has to be worked through one company at a time before you know whether SB 253 applies, and the revenue test and the nexus test are applied to different things. Whether a company under $1 billion is caught at all is worked through in detail on do I need SB 253 under $1 billion.

The first SB 253 Scope 3 disclosure lands in 2027. Before that, November 10, 2026 is a Scope 1 and Scope 2 filing with no Scope 3 component and no assurance requirement. Treating the 2026 date as a Scope 3 deadline is the most common planning error we see, and it works in both directions: some companies scramble to produce a value chain number a year early, and others assume that clearing 2026 means the hard part is done.

One caveat worth stating plainly, because a lot of published commentary skips it. CARB approved its initial SB 253 and SB 261 regulations on February 26, 2026, withdrew the package from the Office of Administrative Law in June 2026 to make clarifying changes, published proposed modifications on July 27, 2026 and ran a further comment period before resubmitting. That package has not yet been approved by OAL. The November 10, 2026 statutory deadline is firm regardless, but the fee amounts, the templates and the recurring deadline language inside the regulations remain proposed rather than final. Anything you read quoting an exact SB 253 fee as settled is ahead of the record. The current position is tracked on California climate disclosure software and SB 253 reporting software.

You may also still find sources giving the first SB 253 report as due August 10, 2026. That was the original date and it moved. CARB announced a three month extension in June 2026 and the operative date is November 10, 2026.

Not to participate, but yes to score well. All three programs are voluntary in the sense that no law compels you to join, and all three become effectively compulsory the moment a customer or an investor makes participation a condition. Each sets a different Scope 3 bar, and the strictest one should drive how you build the inventory.

Read those three rows together and a useful conclusion falls out. The strictest Scope 3 completeness requirement facing a typical US company is not a regulation at all. It is SBTi criterion C5, which caps what you may leave out of the Scope 3 inventory at 5%, combined with C6 measuring target coverage against reported plus excluded emissions. Build the inventory to that standard once and CDP, EcoVadis and a 2027 SB 253 filing are all satisfied by the same underlying data. Build it to the loosest requirement and you will rebuild it at least twice.

There is a second, quieter driver. CDP reported requesting environmental data from more than 45,000 suppliers on behalf of its supply chain members in 2025. A supplier receiving that request is exempt from the CDP administrative fee if the request came only through the supply chain program, and is still scored. Being asked by a customer is now a more common trigger for a first Scope 3 inventory than any statute. That position is covered on supplier emissions reporting software.

Fifteen categories, defined by the GHG Protocol Corporate Value Chain (Scope 3) Standard, split into eight upstream and seven downstream. A complete report states, for each category, either a quantified figure with the method used or a documented reason the category is not relevant. Saying nothing about a category is not the same as reporting it as zero, and the programs above treat the two very differently.

The category boundaries themselves are where most first inventories go wrong, particularly the line between category 1 purchased goods and services and category 2 capital goods, which follows your own capitalization policy rather than any rule in the standard. Each category is worked through on the 15 Scope 3 categories, and the calculation mechanics on how to calculate Scope 3 emissions.

Activity data multiplied by an emission factor, summed by category. For a first inventory in the US, the practical starting point is spend, because purchase records already exist and supplier-specific data almost never does. The reference dataset is the EPA Supply Chain Greenhouse Gas Emission Factors, version 1.3, which covers 1,016 US commodities mapped to six-digit 2017 NAICS codes, was published on July 5, 2024 using 2022 economic data, and is expressed in kilograms of CO2e per 2022 US dollar.

Two details in that dataset change the answer materially. The file contains a without-margins set and a with-margins set, and the without-margins version comes first. Against accounts payable data you want the with-margins factors, because what you paid includes wholesale and retail margins and transport, and the without-margins factors systematically understate category 1. The second is that a spend-based figure inherits the behavior of prices: negotiate a 10% discount with no change in what you buy, and your reported emissions fall 10%. That is a real limitation, not a bug to hide, and it is why spend-based numbers are a screening method that you then replace category by category with supplier-specific data where the amounts justify it.

Global warming potentials are worth checking before you start rather than after. EPA Table A-1 under the GHGRP uses AR5 values, with methane at 28 and nitrous oxide at 265, while CDP expects AR6, with methane at 29.8 and nitrous oxide at 273. Reporting the same inventory into both without noting which set you used is a straightforward way to produce two different numbers and no explanation for the gap. The choice between factor sets is worked through on which EPA emission factors to use.

The hard part of Scope 3 reporting is not the arithmetic, it is producing a complete, categorized, traceable set of activity data from records that were never organized for this purpose. Every purchase invoice, utility bill, fuel card statement and freight document already sits in accounts payable. Classifying those lines into GHG Protocol scopes and categories is what turns a year of spend into a screened inventory across all fifteen categories, which is the thing that tells you whether SBTi C4 applies, where CDP EC-CC17 coverage will come from, and whether an EcoVadis submission clears 95%.

Our approach starts there, from the documents rather than from a blank questionnaire, and keeps the source document attached to each figure so the number can be traced back when a reviewer asks. That traceability is the same property assurance is priced on, which matters as soon as SB 253 assurance or an SBTi Category A limited assurance requirement enters the picture.

The product is in early access. The classification demo above is live and does what it says. Capabilities beyond it are described as planned. For a direct comparison of tool types, see Scope 3 emissions software, and for an honest view of the wider market, best carbon accounting software.

Frameworks overlap enough that teams assume one dataset serves all of them, then discover late that it does not. Three differences do most of the damage, and none of them are about Scope 3 tonnage.

Assurance is a sampling exercise, not a recalculation. The provider picks lines from your reported total and asks you to show the record behind each one. A figure that cannot be traced back to an invoice, a meter reading or a supplier response fails the sample regardless of how accurate the estimate was.

So the practical test of Scope 3 reporting readiness is not whether you have a number, it is whether you can produce the derivation of any single line in it on request. California phases this in deliberately: no assurance requirement for the 2026 Scope 1 and 2 report, limited assurance following in later cycles, and the statutory step to reasonable assurance in 2030 expressly deferred by CARB to a future rulemaking. Treat the 2030 date as a planning assumption rather than a settled one. What the levels demand is explained in limited versus reasonable assurance, and the five standards CARB accepts in SB 253 assurance requirements. Deciding which categories are material enough to upgrade beyond a spend estimate is covered in Scope 3 materiality assessment.

If you are working out which obligation applies before choosing a tool, start with the rule that reaches you. SB 253 reporting software covers the California filing, EPA GHG reporting the federal program, and CDP reporting software the disclosure most US companies meet first. For the underlying concepts, Scope 3 emissions defines the fifteen categories and the best carbon accounting software for spend-based Scope 3 reporting compares how the available tools handle the spend data most first inventories are built from.