30.09.2026

UK CBAM Guide for Importers: Registration, Rates and Records

Name: Carbonova Build
Brand: Carbonova

Imported steel coils and aluminium ingots on a Teesside quay at dusk, with cranes and industrial plant behind

The UK CBAM starts on 1 January 2027. This guide explains who must register with HMRC, how the £50,000 threshold works, how rates are set, what data you need from overseas producers and how to prepare for the first return in May 2028.

From 1 January 2027, the UK Carbon Border Adjustment Mechanism (CBAM) taxes imports of aluminium, cement, fertiliser, hydrogen, and iron and steel goods on the direct emissions embodied in them. You must register with HMRC once your CBAM imports reach £50,000 over a rolling 12 months, or you expect them to within the next 30 days, and the first return and payment, covering calendar year 2027, are due by 31 May 2028. The work that decides your bill starts now: obtaining verified emissions data from overseas producers and setting up the records HMRC expects.

What applies from 1 January 2027

Legal basis. Part 5 of the Finance Act 2026 creates the tax, and regulations made in 2026, including the Carbon Border Adjustment Mechanism (Administrative Provisions) Regulations 2026, fill in the detail. HMRC administers it.
Sectors. Aluminium, cement, fertiliser, hydrogen, and iron and steel, identified by commodity code. Unlike the EU CBAM, electricity is not covered.
Emissions. The charge applies to direct emissions embodied in the goods, plus those embodied in relevant precursors for complex goods.
Accounting period. The calendar year. The first runs from 1 January to 31 December 2027.
Rates. One rate per sector, published at the start of each quarter from 1 January 2027. The rate in force on the import date applies, and an illustrative rate is promised for autumn 2026.
Liability. Embodied emissions multiplied by the sector rate give the CBAM charge. Carbon price relief for a qualifying carbon price already paid overseas is then deducted. Unlike the EU system, there are no certificates: you file an online return and pay the tax.

Who must register

You are the importer if you are named on the import declaration, even when a customs broker, freight forwarder or agent completes it for you. Businesses established outside the UK can be liable too, and the UK CBAM applies in Northern Ireland as it does in Great Britain. From 1 January 2027 there are two tests, and the earlier date applies:

Forward-looking: you expect to import £50,000 or more of CBAM goods within the next 30 days.
Backward-looking: on the first day of each month, you check whether you imported £50,000 or more in the previous 12 months. If so, you are liable from the date your imports reached £50,000.

Imports before 1 January 2027 do not count. Neither do goods for private use, goods of UK origin, goods under Returned Goods Relief, temporary admission goods with full duty relief, or goods held in special procedures such as customs warehousing, inward processing or a freeport customs site until they are released into free circulation. HMRC says its registration service will open by 1 January 2028.

Data you need from overseas producers

Actual emissions: the producer's emissions intensity for each good, in CO2e per tonne or functional unit, verified by a qualifying verifier accredited against ISO/IEC 17029:2019 and ISO 14065:2020 by an eligible accreditation body.
Default values: one per CBAM good, to be published on GOV.UK before the scheme starts, for use when you have no verified actual data.
Carbon price evidence: to claim relief, verified evidence of the effective carbon price paid in the country of production under a qualifying scheme, plus the exchange rate used.

Records to keep

Keep records in written or electronic form for six years from the later of the date they were created or the end of the accounting period they relate to. They include the eight-digit commodity code and description, the customs clearance date, value, net mass in kilograms, proof of origin, evidence for any exemption, the verification report or summary behind any actual emissions, and carbon price relief calculations with exchange rates. Failing to keep records can lead to a £500 fixed penalty.

Steps to take before 1 January 2027

Classify your imports. Check recent import data against HMRC's in-scope commodity code lists and flag every CBAM line.
Model the threshold. Estimate when your rolling 12-month CBAM imports will reach £50,000 and whether the 30-day test could apply in January 2027.
Map your producers. For each line, identify the installation that made the goods, not just the trader that sold them.
Request verified data now. Ask for emissions intensity per good and whether the producer can have it verified by an accredited verifier. Where it cannot, plan to use default values.
Collect carbon price evidence from producers that pay a carbon price at home.
Update contracts to cover data delivery, verification, cost allocation and access to records.
Set up your record-keeping trail and a quarterly routine to apply the rate in force on each import date.

Common mistakes

Assuming your customs agent is the liable importer. It is the person named on the declaration.
Copying EU CBAM processes without checking the differences: the UK uses a £50,000 value threshold rather than the EU's 50-tonne mass threshold, excludes electricity and works through a tax return rather than certificates.
Waiting for default values and neglecting supplier data. Arranging verification takes time.
Collecting figures from traders rather than from producing installations.
Counting on a UK–EU carbon market link. Talks to link the two emissions trading systems are under way, and a link would bring mutual CBAM exemption, but none was in force as of mid-2026.

How Carbonova helps

Brazil-based Carbonova builds Carbonova CarbonOS, an AI-agent platform for greenhouse gas inventories, CBAM embedded-emissions data and regulatory reporting. For UK importers, CarbonOS brings in import data from your ERP, collects data from overseas suppliers, organises embedded emissions by installation and product, and keeps the evidence and data lineage behind each figure, including whether it rests on verified actual data or a default value. That makes the numbers in your return traceable to source. Learn more on our regulatory compliance page.

Carbonova is a software provider. It does not file returns with HMRC, act as your customs agent or verify emissions: verification comes from accredited verifiers, and you remain responsible for your return.

When do I need to register for the UK CBAM?

From 1 January 2027, you are liable to register when you expect to import £50,000 or more of CBAM goods within the next 30 days, or when your imports over the previous 12 months reach £50,000, whichever comes first. HMRC says registration will open by 1 January 2028, and the first return and payment, for 2027, are due by 31 May 2028.

How is the UK CBAM rate set?

The government sets one rate per sector and publishes it at the start of each quarter from 1 January 2027. It is based on average UK ETS auction clearing prices, adjusted for the share of sector emissions still covered by free allowances. Your charge is embodied emissions multiplied by the rate in force on the import date, minus any carbon price relief.

Can I use default values instead of supplier data?

Yes. One default value per CBAM good will be published on GOV.UK before the scheme starts, for use when you do not hold verified actual data. Compare both before deciding, because a default value may not reflect a specific producer's performance.

If you import CBAM goods into the UK and want producer data and records in order before January, book a demo to see how CarbonOS handles it.