UK SRS S2: what your big customers will ask suppliers

UK SRS S2 tells listed companies to measure their Scope 3 emissions with the GHG Protocol and to prefer data from their own suppliers over industry averages, and verified data over unverified. From 2027, expect large customers to ask for your Scope 1 and 2 emissions for a stated 12-month period, the share that relates to them, your method and factors, how the figures were checked, and your targets.

Updated 19 October 2026 by the Carbon Recycling team. Figures use the official UK government conversion factors and are checked against the current gov.uk guidance.

Why a standard you don't report under affects you

UK SRS S2 is the UK's climate disclosure standard, published in February 2026. Under FCA rules finalised in September 2026, most UK listed companies report against it, on a comply or explain basis, for accounting periods starting on or after 1 January 2027. They get one year's relief from Scope 3, so for a calendar-year company the first Scope 3 figure covers 2028. The government is consulting until 30 November 2026 on whether large private companies should follow. Our UK SRS guide covers who reports and when.

You are not in scope. But a listed customer's Scope 3 includes everything it buys, so your emissions become part of its report. That is why the questions arrive.

What the standard tells your customer to prioritise

UK SRS S2 doesn't dictate where Scope 3 data comes from, but it sets out a measurement framework (paragraphs B38 to B57). The company must prioritise inputs with these characteristics, and then disclose how much of its Scope 3 is based on them:

UK SRS S2 asks for	What your customer will ask you
Data from specific activities in the value chain, including from suppliers (primary data)	Your own emissions figures, and the share that relates to them
Timely data that represents the country and technology involved	Your reporting period, and which factors you used (for UK activity, the government's factors for that year)
Verified data, internally or externally	Whether and how your figures were checked
Estimates built from activity data and emission factors, where emissions can't be measured directly	Whether your figures come from activity data, such as meter readings, bills and fuel records, or from spend

The standard also lets your customer use your figures if your year ends on a different date, provided they are your most recent and cover the same length of period. And it expects a company to look at climate risks across its value chain, including suppliers, so some questionnaires will ask about yours: see climate risk for small suppliers.

What happens if you don't answer

Your customer still has to report, so it estimates. The usual fallback is a spend-based estimate: the money it spent with you multiplied by an industry average. Take an illustrative cleaning contractor with £2,000,000 turnover, one of whose customers spends £200,000 a year with it. With the Defra and the University of Leeds multiplier for cleaning and grounds maintenance (2023 data, 0.13808 kg CO2e per £), the customer would record 27.62 tonnes CO2e. That figure describes an average firm in the industry, including its supply chain. It doesn't describe you, and it can't show anything you have done to cut emissions.

Now the contractor's own figures. With 30,000 kWh of electricity, 40,000 kWh of gas and 6,000 litres of van diesel, its 2026 Scope 1 is 22.79 tonnes and its location-based Scope 2 is 3.93 tonnes. The customer is 10% of turnover, so its allocated share of Scope 1 and 2 is 2.67 tonnes CO2e. The two numbers measure different things, so don't present one as a correction of the other. Send your Scope 1 and 2, the allocation and the method, and say which Scope 3 categories you have measured, so the customer can see what is covered. If you switch the vans to electric, the next allocation shows it. An industry average never will.

A checklist before you reply

Scope 1 and 2 in tonnes CO2e, for a stated 12-month period. Give Scope 2 location-based, the basis UK SRS S2 uses for Scope 2, and market-based too if you are on a renewable tariff. Our post on green tariffs explains the difference.
The share allocated to the customer, and the basis, such as revenue.
The method: GHG Protocol, UK government conversion factors and the year of the factors.
Data sources, such as meter readings, bills and fuel cards, and how the figures were checked. Don't call them verified unless they were.
Any Scope 3 you measure, by category.
Your targets and plan. A Carbon Reduction Plan answers most of this, and our post on transition plans for small firms covers what to add.

For the wider etiquette of these requests, what is reasonable to ask and what isn't, see supplier carbon data requests.

How Carbon Recycling helps

Carbon Recycling calculates your Scope 1, 2 and 3 from bills, fuel cards and travel records with the UK government factors, and shows location-based and market-based Scope 2 side by side. Every line keeps the factor and its ID, so a customer or auditor can trace it. The free supplier questionnaire answer bank fills in model answers from your figures, including the revenue-based share for one customer, worked out the same way as the example above.

Frequently asked questions

Do small suppliers have to report under UK SRS?

No. UK SRS applies to listed companies from 2027, on a comply or explain basis, and may later extend to large private companies. No SME is required to report under it. It reaches suppliers through their customers' Scope 3 figures.

When will customers start asking for UK SRS data?

Listed companies report for accounting periods starting on or after 1 January 2027, with relief from Scope 3 in the first year. For a company with a calendar year, the first Scope 3 figure under UK SRS covers 2028. Many will start asking suppliers well before that, to test their process.

Why does my customer want my own figures rather than an estimate?

UK SRS S2 tells companies to prioritise data from specific activities in their value chain, including figures from suppliers, over industry averages. Your figures also show any reductions you have made, which an average can't.

Do my figures need to be verified?

No, but UK SRS S2 asks companies to prioritise verified data and to say how much of their Scope 3 uses it. Verification can be internal or external, including cross-checking against other sources. Say honestly how your figures were checked.

My financial year is different from my customer's. Is that a problem?

Usually not. UK SRS S2 lets a company use a supplier's figures for a different period, as long as they are the most recent available and cover the same length of time, normally 12 months. Always state the period your figures cover.

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