"My EU CBAM report covers my UK obligations too."

Why the two don't interoperate

EU CBAM runs under EU law, with its own definition of covered goods, its own default values, its own certificate-purchase mechanism, and its own verification standard. UK CBAM is a distinct tax created by the Finance Act 2026, charged on the emissions embodied in CBAM goods when they're imported into the UK, calculated through HMRC's own eight-step methodology under the draft Emissions and Verification Regulations 2026. An EU CBAM certificate purchase, declaration, or payment has no legal effect on a UK CBAM liability, and a UK CBAM filing has no legal effect on an EU CBAM obligation.

Where it does help: if you've already been collecting facility-level emissions data from a supplier for EU CBAM reporting, that relationship and that data are a genuine head start — and this isn't just our read of the situation. HMRC's own guidance, published 16 July 2026, states that the UK's monitoring and verification methodology is "broadly designed to support interoperability with the EU CBAM, helping to reduce administrative burdens, and recognising where there are similar characteristics across UK and EU carbon pricing." Verified actual-emissions figures gathered for one regime are frequently reusable as the underlying evidence for the other — but the figures still have to be run through the UK's own calculation steps (monitoring period, conversion to CO₂e, precursor emissions, weight, emissions intensity) and verified by a UK-recognised, GACI-accredited verifier before they count for UK CBAM.

Importers trading with both the EU and UK markets need to run both calculations separately, even where the underlying supplier and product are identical.