UK CBAM guide
UK CBAM vs EU CBAM: what's actually different
A tax versus a certificate scheme, £50,000 versus 50 tonnes, different deadlines and different default values — a verified side-by-side for businesses facing one or both.
Plenty of UK businesses met the acronym CBAM through the EU scheme — as exporters filling in customers' data requests, or through group companies importing into the EU. The instinct that follows is dangerous: "we've seen CBAM before, so we know what the UK one involves." The two regimes share a goal and a name, and almost nothing else that matters operationally.
The one-paragraph version
The EU CBAM is a certificate scheme: importers into the EU need authorisation, buy certificates priced off the EU ETS, and surrender them against an annual declaration of embodied emissions. The UK CBAM is a tax: importers into the UK register with HMRC, self-assess on a return, and pay money. Different thresholds (mass vs value), different emissions scope, different default-value philosophies, different verification plumbing, different deadlines. If you face both, you run two compliance processes — most of the supplier data collects once, but it is used differently on each side.
Side by side
| UK CBAM | EU CBAM | |
|---|---|---|
| Instrument | A tax, self-assessed via HMRC returns. No certificates. | Certificates bought and surrendered, plus an annual declaration via the CBAM Registry. |
| Status | Law (Finance Act 2026); liability from 1 Jan 2027; operational regulations being finalised in 2026. | Live — definitive regime since 1 Jan 2026, after the 2023–25 transitional reporting phase. |
| Sectors | Iron & steel, aluminium, cement, fertilisers, hydrogen. No electricity. | The same five plus electricity; an extension to ~180 downstream steel and aluminium products is proposed from 2028. |
| Threshold | £50,000 (customs value) — rolling 12-month test plus a 30-day forward test. | 50 tonnes net mass per importer per calendar year (doesn't apply to electricity or hydrogen). |
| Pre-approval | None — register after you trigger (by 31 Jan 2028 for 2027 triggers). | Yes — "authorised CBAM declarant" status is required to import above the threshold. |
| Emissions scope | Direct + precursor emissions; indirect (electricity) excluded until 2029 at the earliest. | Direct + indirect in principle, but direct-only for iron & steel, aluminium and hydrogen; cement and fertilisers include indirect. |
| Default values | One value per good, globally uniform (publication due before 2027). | Values per product and per country, tilted against high-intensity origins. |
| Price | Quarterly government-set rate per sector, from UK ETS auction prices net of free allocation. | Certificate price tracks EU ETS auction prices (weekly basis from 2027). |
| First hard deadlines | Register by 31 Jan 2028; first return and payment 31 May 2028 (covering all of 2027). | First annual declaration and surrender: 30 September 2027 (covering 2026). Certificate sales open 1 February 2027. |
| Verification | Independent verifiers to ISO/IEC 17029 + ISO 14065, internationally accredited — overseas verifiers acceptable. | Verifiers accredited within the EU framework. |
| Carbon price paid elsewhere | "Carbon price relief" deduction, evidenced and verified, capped at the liability. | Deduction for the carbon price effectively paid in the origin country. |
| Penalties | HMRC penalty regimes; amounts to be confirmed. | Per-certificate penalty aligned to the EU ETS excess-emissions rate (€100/tCO₂e, indexed). |
Four differences that actually change behaviour
1. Cash and calendar. A business inside both regimes pays the EU first: certificate sales open February 2027 and the first EU declaration lands 30 September 2027 — eight months before the first UK return (31 May 2028). Budget accordingly; the UK's gentler first-year calendar is not the pace the EU side runs at.
2. The threshold logic is opposite. The EU exempts by mass (50 tonnes/year — designed to release ~90% of importers while keeping ~99% of emissions); the UK exempts by value (£50,000). A niche importer of light, high-value covered goods can be exempt in the EU and caught in the UK; a heavy, low-value importer can be the reverse. Never assume one regime's answer transfers.
3. Default values punish differently. EU defaults vary by origin country and lean punitive for high-intensity origins; the UK plans a single global value per good. Which side makes real supplier data worth chasing hardest depends on your origin mix — but the UK's "no advantage over actual data" signal means neither regime intends defaults to be the comfortable option.
4. There is no EU-origin free pass — in either direction. UK importers buying from the EU still face UK CBAM on those goods (with relief for carbon prices actually paid under the EU ETS, evidenced and verified — not an exemption). UK exporters into the EU pay EU CBAM. The two sides committed in May 2025 to negotiate linking their emissions trading schemes, which — once fully in force — is expected to bring mutual CBAM exemptions. As of our review date, no agreement has been concluded: plan on goods being chargeable, and treat linkage as upside. We track this closely and will update this guide the day it moves.
"We already do EU CBAM" — what transfers and what doesn't
Transfers well: supplier relationships and their willingness to share installation-level data; the concept of embodied emissions and precursors; verified emissions reports (the UK methodology is deliberately designed for broad interoperability with the EU's, and a transition route exists for EU-accredited verifiers).
Doesn't transfer: your EU threshold position; your EU default-value maths; the compliance calendar; the filing process (registry vs tax return); and the emissions scope for cement and fertilisers, where the EU counts electricity emissions and the UK for now does not.
Sources
- Finance Act 2026, Part 5 and HMRC CBAM policy summary (April 2026) — UK side
- Regulation (EU) 2023/956 as amended by Regulation (EU) 2025/2083 — EU side, including the 50-tonne threshold and the September declaration deadline
- European Commission CBAM pages — definitive-regime operation
- UK ETS policy overview (April 2026) — the UK–EU linkage commitment