UK CBAM · live 1 Jan 2027
Your first UK CBAM return, done from your supplier spreadsheets.
From 1 January 2027, UK importers of iron & steel, aluminium, cement, fertiliser and hydrogen face a new HMRC carbon levy — and a supplier-data problem nobody's ops team signed up for. CBAMReturn turns your import ledger and the files your suppliers actually send into a clear liability position and an HMRC-ready return.
Built on the enacted Finance Act 2026 and current draft regulations · Plain English · Made for importers and their customs brokers
UK CBAM starts
1 Jan 2027
Liability accrues on covered imports from day one
Registration threshold
£50,000
Covered goods, rolling 12 months or any 30-day window
Register by
31 Jan 2028
Deadline for anyone who crosses the threshold during 2027
First return and payment
31 May 2028
One return covering the whole of 2027, then quarterly
A tax that arrives as a spreadsheet problem
UK CBAM is charged on the emissions embodied in the goods you import. HMRC won't send a bill — you self-assess, from data that mostly sits with mills, smelters and plants overseas.
Your suppliers hold the numbers
The charge depends on per-installation emissions data from your producers. What actually arrives is PDFs, screenshots and spreadsheets in every format except the one you need — if anything arrives at all.
Defaults fill gaps — at a price you should see
Missing data falls back to government default values, expected to be set so there's no advantage over real numbers. Either way, you need to watch the liability build through 2027 — not discover it in May 2028.
The decisions are one-way
Liability accrues from 1 January 2027. Register by 31 January 2028; first return and payment by 31 May 2028; quarterly after that. And a return filed on default values can't be amended later to use the supplier data you didn't collect.
From messy inputs to a filed return
Step 01
Load your imports
Drop in the import ledger your customs broker already produces. We map the commodity codes, flag every CBAM line, and track your position against the £50,000 threshold month by month.
Step 02
Collect supplier data without the chase
Send each supplier a link, or our template. The portal accepts the files suppliers actually produce, tells you what's missing or unusable, and keeps the evidence trail verification will need.
Step 03
See liability, not surprises
Default versus actual, side by side, with provenance on every line — building quarter by quarter into an HMRC-ready return well before the 31 May 2028 deadline.
Honest note: HMRC's return format isn't final — the secondary legislation is still in draft. Tracking those changes is exactly what CBAMReturn is for, and your filing output still lands well before the first deadline.
Made for the mid-sized importer
The £50,000 threshold catches thousands of businesses that have never needed a carbon team: steel stockholders and fabricators, builders' merchants, aluminium distributors, fertiliser importers, manufacturers buying fasteners, wire, tube and structures from overseas. If that's you, UK CBAM is now a finance-and-ops job — CBAMReturn keeps it that way.
Check your position →Covered sectors
Iron & steel
Bar, sheet, tube, wire, structures, rail · Also screws, bolts, nuts and other fasteners (7318)
Aluminium
Unwrought, plate, foil, profiles, structures · Also doors, windows, containers and other articles (7610–7616)
Cement
Cement, clinker, some kaolinic clays
Fertilisers
Nitrogen fertilisers, ammonia, nitric acid · Pure potassic (PK) fertilisers are excluded
Hydrogen
Imported hydrogen
For customs brokers & freight forwarders
Your clients are about to ask you about CBAM
You file their entries, so every CBAM question will land on your desk from 2027 — but you don't want to build software. Partner with CBAMReturn: referral or white-label, your client relationship, our engine. Early partners shape the product and the commercials.
Questions importers are asking
Is UK CBAM actually law?
Yes. The primary legislation is Part 5 of the Finance Act 2026, which received Royal Assent on 18 March 2026, and it applies to covered goods imported from 1 January 2027. The operational detail sits in HMRC regulations that are still in draft — the government has said final versions will be laid later in 2026. That's why everything on this site is dated and version-marked.
Who has to register for UK CBAM?
The importer — the business named on the customs declaration (or on whose behalf it's made) — once its covered goods pass £50,000. Two tests apply: a rolling 12-month total checked on the first day of each month, and a forward-looking test if you expect £50,000 of covered goods within any 30-day window. Anyone who crosses during 2027 must register with HMRC by 31 January 2028.
What do we actually have to do during 2027?
Three things: track whether and when you cross the £50,000 threshold; collect emissions data from your suppliers (or accept default values); and keep records per import line — commodity code, weight, origin, value. Nothing is filed during 2027, but the return you submit by 31 May 2028 is built entirely from what you collect in 2027, and you can't retrofit supplier data you never gathered.
We already handle EU CBAM — is this the same thing?
No, and the differences bite. The EU scheme is a certificate system with a 50-tonne mass threshold and an annual declaration; UK CBAM is a tax paid to HMRC with a £50,000 value threshold and its own return cycle. Emissions scope, default values and verification rules also differ. Read our UK vs EU guide for the full comparison.
What if our suppliers won't share emissions data?
You fall back on government default values — one per type of good, published before the regime starts. Defaults keep you compliant but are expected to be set so there's no advantage over real data, and the rules don't let you amend a return later to swap defaults for actuals. The practical move is to request data early, see which suppliers respond, and know exactly what the gap is costing you — which is what CBAMReturn is being built to show.
Is CBAMReturn tax advice?
No. CBAMReturn is software plus plain-English guidance. We keep our regulatory content verified against primary sources and dated, but it's general information — for decisions about your own liability, talk to your accountant or adviser.
Longer answers, with sources: the complete UK CBAM guide →
Be ready before it's mandatory
CBAMReturn launches ahead of the 2027 start. Join the waitlist for early access, the free supplier emissions data template, and plain-English alerts when the rules move.