UK CBAM: 2027 Rates, the £50,000 Threshold and Key Dates
From 1 January 2027 the UK CBAM puts a carbon price at the border on imports of aluminium, cement, fertiliser, hydrogen, and iron and steel. It is structured as a tax, not a certificate scheme — the liability sits with the UK importer, who must register with HMRC, report the emissions embodied in each shipment, and pay the gap between the carbon price already paid abroad and the price a UK producer faces under the UK ETS.
The charge is calculated on carbon your supplier emitted — which means the data problem is your supplier’s, but the bill is yours.
The UK CBAM is a carbon tax on imported aluminium, cement, fertiliser, hydrogen, and iron and steel from 1 January 2027. Importers above £50,000 register with HMRC and pay a quarterly rate per tonne of CO₂e: £1.45 to £9.79 on HMRC’s October 2026 illustrative figures.
What the UK CBAM is and why it exists
The UK Carbon Border Adjustment Mechanism is a tax on the carbon emissions embodied in certain imported goods. Its purpose is to neutralise carbon leakage — the risk that domestic decarbonisation policy simply pushes carbon-intensive production overseas, where it is cheaper to emit, rather than reducing emissions overall. A UK steel producer pays for its emissions under the UK ETS; an overseas competitor exporting the same steel into the UK has historically faced no equivalent cost. CBAM closes that gap by applying a comparable charge at the border.
The legal foundation is the Finance Act 2026, which received Royal Assent on 18 March 2026. It establishes CBAM in primary legislation, grants HMRC the statutory powers to run and enforce the mechanism, and sets the framework for the secondary legislation that fills in the operational detail. CBAM takes effect on 1 January 2027.
The detail is now in law. HM Treasury made the Administrative Provisions Regulations (SI 2026/802, registration, returns and records), the Calculation of CBAM Rate and Determination of Carbon Price Relief Regulations (SI 2026/809) and the Transitory Provision Regulations (SI 2026/830, first-year dates) in July 2026, followed by the Emissions and Verification Regulations (SI 2026/995). All come into force on 1 January 2027. On 16 October 2026 HMRC published illustrative rates, the default emissions values for every in-scope good, and its monitoring and verification guidance.
The UK chose to run CBAM as an indirect tax administered by HMRC, rather than as a tradable-certificate scheme like its EU counterpart. The practical consequences are concrete: there is no certificate to buy and surrender, the liable person self-assesses the charge on a tax return, the rate is published by HMRC rather than discovered in a market, and the whole regime plugs into existing customs and tax administration. For importers, CBAM looks and behaves like a duty calculated on embodied carbon.
Two design decisions shape the launch. First, indirect emissions — those from the electricity consumed in production — are out of scope at the 1 January 2027 start and delayed until 2029 at the earliest, to preserve the Energy Intensive Industries Compensation Scheme. Second, the glass and ceramics sectors, originally proposed for inclusion, were dropped before launch on feasibility grounds, though the product scope will be kept under review beyond 2027.
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UK CBAM rates for 2027 and what they cost per tonne
HMRC published illustrative CBAM rates on 16 October 2026. They show what the rates would be from 1 January 2027 on current data. They are not a tax liability and not a forecast: the rates that apply to imports from January to March 2027 will be published before the end of 2026, then at the start of every quarter. The rate that applies is the one for the quarter in which the good was imported.
| Sector | Illustrative rate (£/tCO₂e) | Example good (commodity code) | HMRC default value (tCO₂e/t) | Charge per tonne at that default |
|---|---|---|---|---|
| Iron and steel | £9.69 | Hot-rolled flat steel, coils under 3 mm (7208 39 00) | 3.468 | £33.60 |
| Aluminium | £9.79 | Aluminium alloy hollow profiles (7604 21 00) | 3.894 | £38.12 |
| Cement | £8.78 | Portland cement, grey (2523 29 00) | 1.375 | £12.07 |
| Fertiliser | £1.45 | Ammonium nitrate, solid (3102 30 90) | 2.600 | £3.77 |
| Hydrogen | £9.24 | Hydrogen (2804 10 00) | 28.378 | £262.21 |
Charge per tonne is the default value multiplied by the illustrative rate. Verified actual emissions from your supplier replace the default, and a qualifying carbon price paid abroad is deducted (see carbon price relief). Default values are from HMRC’s default values tables, published the same day.
Average UK ETS auction price for July to September 2026: £58.15. UK cement producers’ direct emissions covered by free allowances: 87.1%. The 2027 phase-out factor: 97.5%. Rate = £58.15 × [1 − (87.1% × 97.5%)] = £8.78 per tonne of CO₂e. The rates are low because UK producers in these sectors still receive most of their allowances free; as free allocation is phased out, the rate rises toward the full UK ETS price. Fertiliser’s £1.45 implies that free allowances cover almost all of that sector’s direct emissions.
To estimate a full consignment with your own quantities, intensities and overseas carbon price, use the UK CBAM calculator. The step-by-step method is in the UK CBAM methodology.
Where UK CBAM sits in the carbon-pricing stack
CBAM is not a standalone tax — it is the border extension of the UK ETS. Its entire purpose is to import the domestic carbon price to the edge of the market, so understanding it means understanding the layers it rests on. The rate is derived from the UK ETS; the scope boundaries mirror UK ETS system boundaries; and the emissions data it requires is the same embodied-carbon data that feeds value-chain accounting.
CBAM is the UK ETS price, applied at the border, to the carbon embodied in imports — minus whatever carbon price the exporting country already charged. Everything else in the mechanism is administration around that core equation.
Scope — sectors, gases, and exclusions
CBAM applies only to specified goods in five sectors, identified by commodity code in HMRC’s list of in-scope goods. The sector is necessary but not sufficient — a good is in scope only if its commodity code is listed, which is why importers must check at the code level, not the sector level.
| Sector | In scope from 1 Jan 2027 | Greenhouse gases covered |
|---|---|---|
| Iron and steel | Yes — specified commodity codes | CO₂ |
| Aluminium | Yes — specified commodity codes | CO₂ and perfluorocarbons (PFCs) |
| Cement | Yes — specified commodity codes | CO₂ |
| Fertiliser | Yes — specified commodity codes | CO₂ and nitrous oxide (N₂O) |
| Hydrogen | Yes — specified commodity codes | CO₂ |
| Glass and ceramics | No — dropped before launch; under review for later inclusion | n/a at launch |
| Electricity | No — excluded from UK CBAM scope (unlike EU CBAM) | n/a |
What is excluded within the in-scope sectors
Three exclusions matter at the goods level. Scrap products in the aluminium and iron-and-steel sectors are out of scope, identified by their own commodity codes. Indirect emissions — from electricity consumed in production — are out of scope until 2029 at the earliest. And goods imported for non-business purposes fall outside CBAM entirely; the mechanism applies only to goods imported in the course of business.
“My product is steel” does not settle whether CBAM applies. The determinant is the specific commodity code against HMRC’s list of in-scope goods. Codes can move with changes to the UK Tariff, and HMRC has committed to updating the CBAM code list in step with customs legislation so goods do not drift in or out of scope unintentionally. An importer’s first compliance task is a commodity-code review of its actual import lines — not a sector self-assessment.
The liable person and the £50,000 threshold
CBAM liability sits with the importer of the CBAM goods — not the overseas manufacturer. Where goods are subject to customs controls, the liable person is the one responsible for the customs declaration, or the person on whose behalf it is made. Where there are no customs controls, it is the person on whose behalf the goods are imported. Tax agents can be appointed to submit returns, but they cannot register on the liable person’s behalf, and no liability attaches to the agent.
A person must register with HMRC for CBAM once the total value of CBAM goods they import meets or exceeds £50,000 over the relevant period. Two tests apply: a backward-looking test on the previous 12 months, and a forward-looking test on whether the value over the next 30 days is expected to reach the threshold. If both tests are met, liability starts from the earlier date. Importers below £50,000 are outside the regime.
Ordinarily a liable person has 30 days from becoming liable to register. In the first year, this is relaxed: for CBAM goods imported during the 2027 calendar year, businesses have until 31 January 2028 to register (SI 2026/830). HMRC’s registration service opens on 1 January 2028, so anyone liable in 2027 cannot register before then: keep all records of CBAM goods from the first import so the first return can be completed. Importers below the threshold should also keep records, because HMRC expects them to be able to show they are not liable.
Once registrable, the liable person submits an online CBAM return after each accounting period and pays any tax due. Nil returns are required even in periods with no liability, unless the person has de-registered. The obligation is continuous — an importer must keep under review whether it has crossed the threshold.
How the CBAM charge is calculated
The CBAM charge reduces to a single equation applied per type of good, then summed across a return. Each element is defined in the legislation and guidance, and each is a place where the calculation can go wrong.
For each type of CBAM good: CBAM liability = (embodied emissions × sector CBAM rate) − carbon price relief. Embodied emissions are the verified emissions intensity multiplied by the weight imported; the sector rate is the quarterly HMRC rate benchmarked to the UK ETS; carbon price relief deducts any qualifying overseas carbon price already paid on those emissions. Total relief cannot exceed the liability — CBAM does not generate a refund.
The CBAM rate — UK ETS benchmark and free-allocation adjustment
The rate is the part of CBAM most often misunderstood, because it is not simply the UK ETS price. There is a single rate per sector, set with reference to the effective carbon price a UK producer in that sector actually faces — which is the headline UK ETS price reduced by the free allowances those producers receive. HMRC constructs each quarterly rate from three components.
The mean of all UK ETS auction clearing prices for the relevant quarter. If every auction in a quarter fails to clear, the last positive average is carried forward. This is the headline domestic carbon price the rate starts from.
The headline price is reduced to reflect the free allowances UK producers in that sector receive — because a domestic producer does not pay the full ETS price on freely allocated emissions. The adjustment is 1 minus the average proportion of sectoral direct emissions covered by free allowances, using UK ETS baseline data (2019, 2022, and 2023 for sub-installations producing CBAM goods).
The FA adjustment is multiplied by a reduction factor that tracks the phase-out of free allowances under the UK ETS — free allocation for CBAM sectors is being phased out over an indicative nine years from 2027. As free allowances fall, the FA adjustment shrinks and the CBAM rate rises toward the full ETS price.
The CBAM rate is deliberately calibrated to the carbon cost a UK producer actually bears, not the sticker UK ETS price. Early on, generous free allowances mean UK producers pay only a fraction of the headline price, so the CBAM rate is correspondingly discounted. As free allocation phases out over the nine-year window, the discount narrows and the effective CBAM rate climbs toward the full ETS price — independent of any movement in the auction price itself. Importers modelling future CBAM cost cannot hold the rate constant; the reduction factor is engineered to increase it.
Embodied emissions — actual data, defaults, and precursors
The CBAM charge is levied on embodied emissions, so how those emissions are determined is the heart of the importer’s obligation. There are two routes, and a third complication for complex goods.
Verified data on the emissions actually generated during production of the imported good. This is the route HMRC prefers and the one that aligns with the data an EU CBAM declarant must collect. It requires the importer to obtain emissions information from the overseas producer, calculated within the relevant system boundaries and verified. Actual data almost always produces a lower, fairer charge than the default for a cleaner-than-average producer — which is the entire incentive for engaging suppliers early.
Where verified actual data is unavailable, the importer uses HMRC’s default values, published on 16 October 2026: one value per in-scope good, the same whatever the country of origin. Under HMRC’s draft force of law notice they apply from 1 January 2027 to 31 December 2028 and include a 10% mark-up in every sector except fertiliser. From 2029 the UK plans country-specific defaults, one value per good per country. A single global default is deliberately conservative: a low-carbon producer that cannot supply verified data is taxed as though it were average, which penalises clean production that lacks the paperwork.
For a complex CBAM good, the charge includes the emissions embodied in relevant precursor goods — in-scope CBAM goods used as inputs to its production. Steel used to make a more complex steel product, or clinker used to make cement, carries its own embodied emissions forward into the final good. This mirrors the UK ETS treatment and means the embodied-emissions figure for a complex good is a sum across its in-scope inputs, not a single production-step measurement.
System boundaries define which direct emissions and production processes count. UK CBAM system boundaries reflect UK ETS system boundaries — so, for example, emissions from burning natural gas to heat raw materials fall in scope where the equivalent UK ETS boundary captures them. Direct emissions, for CBAM, means only those identified as relevant within the established boundaries, not every emission associated with the good’s existence.
Both the actual-emissions route and any carbon-price-relief claim depend on verified evidence. The onus is on the liable person — the importer — to hold verification documents, including for parts of the supply chain it did not produce. An importer cannot claim a low actual-emissions figure, or a deduction for an overseas carbon price, on an unverified assertion from a supplier. The monitoring and verification rules are set by the Emissions and Verification Regulations (SI 2026/995) and HMRC’s technical guidance of 16 October 2026; build the supplier-data and evidence trail to that standard from the first import, because retrofitting it afterwards is far harder.
Carbon price relief — deducting overseas carbon prices
Carbon price relief is the mechanism that stops a good being charged twice for the same carbon. If the embodied emissions in an imported CBAM good were already subject to a qualifying overseas carbon price, the importer can deduct that amount from the CBAM liability — the UK CBAM only charges the difference between the overseas price and the effective UK price.
| Requirement | What it means in practice |
|---|---|
| Qualifying scheme type | A carbon tax, an emissions trading scheme, or a scheme that prices emissions embodied in imported goods (i.e. another CBAM). It must be administered by or on behalf of a tier of government. |
| Explicit / deductible price | The scheme must place a price directly or indirectly on emissions. Only deductible carbon prices count — implicit pricing through general energy taxes or regulation does not qualify. |
| Verified evidence | The importer must hold verification documents and the information needed to calculate the relief. Evidence must show a liability was incurred — not necessarily that it has already been paid. |
| Multiple schemes / installations | Relief can be claimed where a good was subject to more than one qualifying scheme, or produced across more than one installation in the same jurisdiction. |
| Schemes HMRC lists as qualifying | 16 as of 19 June 2026: the EU ETS, Swiss ETS, China national ETS, India CCTS, Japan GX-ETS, Korea K-ETS, New Zealand ETS, Kazakhstan ETS, Montenegro ETS, Canada federal OBPS, Australia Safeguard Mechanism, and carbon taxes in Chile, Serbia, Singapore, South Africa and Taiwan (carbon fee). The list is not exhaustive. Emissions covered by free allowances abroad do not qualify, and any rebate reduces the relief. |
| Relief cap | Total relief claimed cannot exceed the CBAM liability for the good. CBAM never refunds an overseas price higher than the UK charge — it only nets to zero. |
Carbon price relief means a supplier in a well-regulated market — one with a real carbon price — produces a lower net CBAM charge than an identical supplier in an unpriced market. The mechanism rewards sourcing from carbon-priced jurisdictions, provided the importer can evidence the price paid. For procurement teams, the overseas carbon price is now a line item worth diligencing, not just the headline unit cost.
Accounting periods, returns, and the payment timeline
CBAM operates on accounting periods, and the first one is deliberately long to give both businesses and HMRC time to bed in. After that, the regime moves to a quarterly cycle.
UK CBAM versus EU CBAM
Many UK importers also export into the EU, or sit in supply chains touching both regimes, so the differences between the EU CBAM and the UK CBAM are operationally important. They share a purpose — pricing embodied carbon at the border to stop leakage — but differ in mechanism, scope, and timing.
| Dimension | UK CBAM | EU CBAM |
|---|---|---|
| Mechanism | Indirect tax; self-assessed on an HMRC return | Certificate scheme; buy and surrender CBAM certificates |
| Effective from | 1 January 2027 (no separate reporting-only phase) | Definitive regime from 1 January 2026 (after a 2023–2025 transitional reporting phase) |
| Sectors | Aluminium, cement, fertiliser, hydrogen, iron & steel | Iron & steel, aluminium, cement, fertilisers, hydrogen, and electricity |
| Electricity | Out of scope | In scope |
| Indirect emissions | Out of scope until 2029 at the earliest | In scope for some sectors (e.g. cement, fertilisers) post-transition |
| De minimis threshold | £50,000 value of CBAM goods over the period | 50 tonnes mass of CBAM goods per year |
| Price basis | Quarterly sector rate from UK ETS, net of free-allocation adjustment | Certificate price tracking the EU ETS auction price |
| Overseas carbon price | Deductible via carbon price relief (verified) | Deductible where a price was paid (documented) |
In May 2025 the UK and the European Commission agreed to work toward linking the UK and EU emissions trading schemes. A linkage agreement is intended to deliver mutual CBAM exemptions — goods traded between the UK and EU in covered sectors would face no CBAM at the border, because both sides would face an aligned carbon price. Negotiations began in 2026; as of 22 October 2026 neither government had published an agreement. Until one is in force, UK exporters to the EU remain subject to EU CBAM, and EU exporters to the UK remain subject to UK CBAM. There is also unresolved complexity around how EU CBAM applies in Northern Ireland under the Windsor Framework. Treat the linkage as a prospect to monitor, not a planning assumption.
The importer’s data problem and the Scope 3 link
The hardest part of CBAM compliance is not the tax mechanics — it is getting verified emissions data out of overseas suppliers. The charge is levied on carbon the supplier emitted, but the liability and the evidence burden fall on the UK importer. An importer that cannot obtain verified actual data is taxed on the conservative default, which is usually higher. The financial incentive to build a supplier-data pipeline is direct and quantifiable.
That pipeline is the same one a company needs for value-chain carbon accounting. The embodied-carbon data CBAM requires from a supplier is, in substance, Scope 3 Category 1 data — emissions from purchased goods. A business that already runs a Scope 3 inventory has most of the supplier-engagement machinery in place; one that does not now has a tax-driven reason to build it.
The supplier emissions figures that determine a CBAM charge are the same figures that populate Scope 3 Category 1 for the importing company’s own GHG inventory and its CSRD or other disclosure obligations. Treating CBAM data collection and Scope 3 data collection as two separate projects duplicates supplier outreach and verification effort. Build one supplier-data programme that serves both: the verified embodied-emissions intensity per product, per supplier, is the shared primitive.
For importers of in-scope goods, GreenCalculus process calculators produce the embodied-emissions intensities CBAM is built on — for example iron and steel, cement and lime, and aluminium PFC process emissions — giving the audit-grade figures a verifier and HMRC can stand behind.
UK CBAM readiness checklist
This checklist tracks readiness across two tracks: the registration-and-administration work an importer owns directly, and the emissions-data work that depends on supplier engagement. The second track is the one with the longest lead time — start it first.
Common compliance errors
Frequently asked questions
The UK Carbon Border Adjustment Mechanism is a tax on the carbon emissions embodied in certain imported goods, designed to prevent carbon leakage by ensuring imports face a carbon price comparable to that paid by UK producers under the UK ETS. It takes effect on 1 January 2027 under the Finance Act 2026, which received Royal Assent on 18 March 2026. It applies to imports of aluminium, cement, fertiliser, hydrogen, and iron and steel, identified by commodity code. The liability sits with the UK importer, who registers with HMRC, reports embodied emissions, and pays a quarterly sector rate less any deductible overseas carbon price.
The official rate for January to March 2027 will be published by HMRC before the end of 2026. HMRC’s illustrative rates of 16 October 2026, based on the July–September 2026 UK ETS price of £58.15, are £9.69 per tonne of CO₂e for iron and steel, £9.79 for aluminium, £8.78 for cement, £9.24 for hydrogen and £1.45 for fertiliser. They are not a liability or a forecast. Rates then change every quarter with the UK ETS price and the phase-out of free allowances.
HMRC’s registration service opens on 1 January 2028. If you pass the £50,000 threshold during 2027, you have until 31 January 2028 to register, and you must keep records of every CBAM import from the start so you can file the first return, for the whole of 2027, by 31 May 2028.
Five sectors are in scope from 1 January 2027: aluminium, cement, fertiliser, hydrogen, and iron and steel. Within these, CBAM applies only to specific goods identified by commodity code in HMRC’s list of in-scope goods — sector membership alone does not put a good in scope. Greenhouse gas coverage is CO₂ for all sectors, plus nitrous oxide (N₂O) for fertilisers and perfluorocarbons (PFCs) for aluminium. Glass and ceramics, originally proposed, were dropped before launch but may be added later. Electricity is excluded from UK CBAM (unlike EU CBAM). Scrap products in aluminium and iron and steel are excluded, and indirect (electricity-related) emissions are out of scope until 2029 at the earliest.
The liable person is the importer of the CBAM goods — usually the person responsible for the customs declaration, or the person on whose behalf goods are imported where there are no customs controls. A person must register with HMRC once the total value of CBAM goods they import meets or exceeds £50,000 over the relevant period, assessed via a backward-looking 12-month test and a forward-looking 30-day test. Importers below £50,000 are outside the regime. Ordinarily registration is required within 30 days of becoming liable, but for goods imported during 2027 businesses have until 31 January 2028. Tax agents can submit returns but cannot register on the liable person’s behalf.
For each type of CBAM good, the charge is embodied emissions multiplied by the sector CBAM rate, less any carbon price relief. Embodied emissions are the verified emissions intensity multiplied by the weight imported, including emissions in relevant precursor goods for complex products. The sector rate is set by HMRC each quarter, benchmarked to the UK ETS price and reduced by a free-allocation adjustment that reflects the free allowances UK producers receive. Carbon price relief deducts any qualifying overseas carbon price already paid on those emissions, with verified evidence — but total relief cannot exceed the liability, so CBAM never produces a refund.
There is a single rate per sector, updated quarterly. It is built from three elements: the average UK ETS auction clearing price for the quarter; a free-allocation adjustment (1 minus the average proportion of sectoral direct emissions covered by free allowances, using UK ETS baseline data for 2019, 2022, and 2023); and a reduction factor that tracks the phase-out of free allowances. Because the rate reflects the carbon price a UK producer actually bears after free allowances — not the headline ETS price — it starts discounted and rises toward the full ETS price as free allocation is phased out over an indicative nine-year window from 2027.
Yes. Where verified actual emissions data is unavailable, importers can use HMRC default values. HMRC published them on 16 October 2026: one value per good, the same for every country of origin, applying from 1 January 2027 to 31 December 2028 with a 10% mark-up in every sector except fertiliser. Country-specific defaults are planned from 2029. However, defaults are deliberately conservative — a single global average typically produces a higher charge than a clean producer’s actual intensity. A below-average-intensity supplier that cannot provide verified data is taxed as though it were average. The cost gap between actual and default is the financial case for collecting verified supplier data, which also aligns with what an EU CBAM declarant must obtain.
Carbon price relief reduces CBAM liability where the embodied emissions in an imported good were already subject to a qualifying overseas carbon price — so the good is not charged twice. A qualifying scheme is a carbon tax, an emissions trading scheme, or another CBAM, administered by or on behalf of a tier of government, that places an explicit price on emissions. The importer must hold verification documents and the information needed to calculate the relief; evidence must show a liability was incurred, though not necessarily already paid. Relief can be claimed across multiple schemes or installations in the same jurisdiction, but total relief cannot exceed the CBAM liability for the good.
The first accounting period is the full 2027 calendar year (1 January to 31 December 2027), with the return and payment due by 31 May 2028 — five months after the period ends, to allow time to assemble supporting emissions data. From 1 January 2028, accounting periods move to calendar quarters. The first two quarterly returns are due by 31 July 2028 and 29 September 2028; from the July–September 2028 quarter, returns and payments are due on the last working day of the second month after the quarter ends. Nil returns are required even when there is no liability in a period, unless the liable person has de-registered.
Both price embodied carbon at the border, but the mechanisms differ. The UK CBAM is an indirect tax self-assessed on an HMRC return; the EU CBAM is a certificate scheme where importers buy and surrender CBAM certificates. The EU CBAM covers electricity and the UK CBAM does not. The UK uses a £50,000 value de minimis threshold; the EU uses a 50-tonne mass threshold. The EU’s definitive regime began on 1 January 2026 after a transitional reporting phase; the UK starts directly on 1 January 2027 with no separate reporting-only phase. Both allow deduction of an overseas carbon price already paid. A UK–EU ETS linkage agreement, under negotiation since May 2025, could create mutual CBAM exemptions for goods traded between the two, but its timing is uncertain.
The verified embodied-emissions data CBAM requires from overseas suppliers is, in substance, the same Scope 3 Category 1 data (emissions from purchased goods) that feeds a company’s own GHG inventory and its CSRD or other disclosure obligations. A business that already runs a Scope 3 inventory has much of the supplier-engagement and verification machinery in place; one that does not now has a direct, tax-driven incentive to build it. The most efficient approach is a single supplier-data programme that captures verified embodied-emissions intensity per product and per supplier, serving CBAM, the GHG inventory, and disclosure together rather than as separate projects.
Build the verified embodied-emissions data UK CBAM runs on. GreenCalculus process calculators output audit-grade Scope 1 process intensities for iron and steel, cement, and aluminium — the same figures that satisfy a CBAM return, a verifier, and your Scope 3 Category 1 inventory.