UK CBAM 2027: HMRC Confirms the Rules for Importers

The UK CBAM now has its final shape. HMRC laid the secondary legislation before Parliament on 13 July 2026 alongside a full guidance package, confirming how the UK Carbon Border Adjustment Mechanism will operate from 1 January 2027. For companies that import into both the European Union and the United Kingdom, this is the point at which dual compliance stops being a planning assumption and becomes a build.

The headline design was already known. What was missing until July was the operational detail: how registration is triggered, how the charge is calculated, what relief is available for carbon already priced abroad, and how long records must be kept.

What HMRC confirmed in July 2026

On 13 July 2026 HMRC laid secondary legislation before Parliament and published the accompanying guidance. Together these set the operational framework for the UK CBAM: registration and deregistration mechanics, the method for calculating the amount payable, the relief and reimbursement arrangements, and the record keeping obligations that sit behind all of it.

The scope is five product categories: aluminium, cement, fertilisers, hydrogen, and iron and steel. Glass and ceramics, which appeared in earlier consultation rounds, remain outside the regime for now.

Registration and the £50,000 threshold

An importer must register once the value of CBAM goods brought into the UK reaches £50,000. Two tests apply, and meeting either one triggers the obligation:

Forward looking. You expect to import £50,000 or more of CBAM goods within the next 30 days.
Backward looking. Your CBAM goods imports over the preceding 12 month period have reached £50,000.

The thresholds apply from 1 January 2027. Registration itself runs through the Government Gateway and must be completed by 31 January 2028 for businesses that crossed the threshold during 2027.

Note the difference in unit from the EU. The UK threshold is monetary and based on customs value, whereas the EU de minimis is a mass threshold of 50 tonnes per year. A business comfortably below the EU threshold on weight can sit well above the UK threshold on value, particularly for hydrogen or high grade alloy products.

Calculating the UK CBAM charge

The UK does not use tradable certificates. The amount payable is calculated directly: the quantity of embodied greenhouse gas emissions, expressed in tonnes of CO₂ equivalent, multiplied by the applicable carbon price published by HM Treasury for that sector and that quarter.

Two consequences follow. There is no purchasing platform to manage and no holding requirement to monitor through the year, which removes the working capital mechanics that dominate the EU regime and its central certificate purchasing platform. In exchange, the rate is set administratively per sector and per quarter, so exposure moves with a published schedule rather than with a traded market price.

Weights are measured excluding packaging, and the underlying import records must support the figure declared.

Carbon price relief and exemptions

Where a carbon price has already been paid in the country of production, carbon price relief reduces the UK liability. Three conditions have to be met together:

The overseas carbon price qualifies under a recognised scheme.
The importer holds a completed verification form from the manufacturer.
An independent verifier meeting the required standards has validated that form.

Separately, goods are outside the charge where they originate in the UK, where returned goods relief applies, or where an equivalent re importation relief is available.

The verification form requirement is the piece most likely to be underestimated. It is a specific document obtained from the overseas manufacturer, not a by product of a supplier questionnaire, and it needs an independent verifier in the chain.

Accounting periods and deadlines

The first accounting period is deliberately long, then the rhythm tightens:

1 January to 31 December 2027. A single 12 month accounting period. The return and any payment are due by 31 May 2028.
From 1 January 2028. Accounting periods follow calendar quarters. Returns and payments fall due on the last working day of the second month after the period ends.
Six years. Records relating to imports from 1 January 2027 must be retained for six years, including for goods the importer treats as exempt.

That last point is worth reading twice. The obligation to keep evidence covers goods you have concluded are out of scope, which means the reasoning behind an exemption decision has to be documented at the time, not reconstructed if HMRC asks in 2032.

How the UK CBAM differs from the EU CBAM

HMRC has described the UK regime as broadly consistent with the EU one, with the treatment of electricity as the notable exception. The methodology for embedded emissions is similar enough that the same supplier data can generally serve both. The compliance architecture around it is not the same.

Instrument. A levy paid with a return in the UK, against purchase and surrender of certificates in the EU.
Threshold. £50,000 of customs value in the UK, against 50 tonnes of goods in the EU.
Scope. The EU includes imported electricity; the UK does not.
Pricing. Quarterly sector rates set by HM Treasury in the UK, against a certificate price derived from EU ETS auction results.
Timing. First UK return by 31 May 2028; first EU annual declaration by 30 September 2027.

Running both regimes without duplicating work

The efficient position is a single emissions dataset feeding two outputs. That works if the data is captured at installation level with its source, method and period recorded, because both regimes ultimately ask the same question about the same tonne of steel. It fails if data is captured as a set of figures pasted into whichever return happened to be due first.

Practical steps for the next twelve months:

Screen your UK import book against the £50,000 threshold on both tests, separately from the EU 50 tonne screen.
Extend supplier data requests to cover UK shipments rather than running a second exercise later.
Add the UK verification form to the same supplier conversation that already covers EU verification access.
Map which entity is the importer of record in the UK, which may not be the entity acting as authorised CBAM declarant in the EU.
Document exemption decisions as they are made, given the six year retention rule.

CBAM Desk keeps supplier emissions data at installation level with a full audit trail, which is what makes one dataset serve two regimes. Our partner network covers the specialist advice where UK and EU obligations interact in a group structure.

FAQ

When does the UK CBAM start?

The UK CBAM applies to goods imported into the United Kingdom from 1 January 2027. There is no transitional reporting period equivalent to the EU one. Liability and record keeping obligations begin on day one, even though the HMRC registration service only opens during 2027 and registration must be completed by 31 January 2028.

What is the UK CBAM registration threshold?

£50,000 of CBAM goods, measured on the customs value rather than on weight. It is tested two ways: forward looking, if you expect to import £50,000 or more of CBAM goods in the next 30 days, and backward looking, if your imports over the preceding 12 months have reached £50,000.

How does the UK CBAM differ from the EU CBAM?

The UK charges a direct levy paid with a return rather than requiring the purchase and surrender of certificates. The threshold is a monetary one of £50,000 rather than the EU de minimis of 50 tonnes. The UK covers aluminium, cement, fertilisers, hydrogen and iron and steel but not electricity, which the EU does include. Rates are set quarterly by HM Treasury per sector.

When is the first UK CBAM return due?

The first accounting period runs for the full 12 months from 1 January to 31 December 2027, with the return and any payment due by 31 May 2028. From 1 January 2028 accounting periods become calendar quarters, with returns and payments due on the last working day of the second month after the period ends.

Can I reuse my EU CBAM supplier data for the UK?

Largely yes at the level of the underlying emissions data, because the UK methodology is broadly consistent with the EU approach. The packaging differs. UK carbon price relief requires a completed verification form from the overseas manufacturer, validated by an independent verifier meeting the required standards, which is a different deliverable from an EU verified CBAM declaration.

Key takeaway

With the July 2026 legislation and guidance in place, the UK CBAM is now a known quantity, and the work of preparing for it can start against firm rules. For importers already deep in EU compliance the marginal effort is modest, provided the supplier data was built as a reusable dataset rather than as a filing. Companies that treat the two regimes as one data problem and two outputs will spend far less than those that run them as separate projects. Get in touch to discuss a dual EU and UK setup, or read our latest CBAM news and analysis.