UK CBAM Arrives in January 2027: What the £50,000 Threshold Means for Small Importers
Will Marshall
Founder
As carbon pricing spreads across major economies, the UK is preparing to extend its own carbon price beyond its borders. The UK Carbon Border Adjustment Mechanism (CBAM) enters into force on 1 January 2027, applying a charge to certain imported goods based on the emissions embodied in their production. For SMEs importing steel, aluminium, cement, fertilisers or hydrogen, it brings a new tax liability, a new reporting obligation, and a set of record-keeping duties that begin on day one.
What Is the UK Carbon Border Adjustment Mechanism?
The UK CBAM is a charge on imported goods, calculated from the greenhouse gas emissions released in producing them. It exists to address carbon leakage — the risk that businesses relocate production, or buyers switch suppliers, to countries with weaker carbon pricing.
UK manufacturers already pay for their emissions through the UK Emissions Trading Scheme. Imported equivalents produced in jurisdictions without a comparable carbon price arrive cheaper as a direct result.
CBAM closes that gap by charging imports a price broadly equivalent to what a UK producer would have paid. The policy intent is competitive fairness rather than revenue generation, though the practical effect for importers is an additional cost on affected goods.
Which Goods and Businesses Does UK CBAM Apply To?
Five sectors are covered from the outset: aluminium, cement, fertilisers, hydrogen, and iron and steel. The scope extends beyond raw commodities to include a range of processed and downstream products, which is where many smaller importers are caught unexpectedly.
The registration threshold sits at £50,000 of CBAM goods, raised from the £10,000 originally proposed. The government estimates this exemption still keeps around 99% of imported emissions within scope while removing the smallest importers from the administrative burden entirely.
The threshold is tested twice over on the first day of each month: a backward-looking test covering the preceding 12 months, and a forward-looking test covering the next 30 days. Crossing either one triggers a duty to register with HMRC.
Responsibility falls on the "liable person" — generally the person in whose name the customs declaration is made. This is a point of frequent confusion. Using a customs broker or freight forwarder does not transfer the liability; the importer remains accountable for registration, returns and payment.
How Is the UK CBAM Charge Calculated?
Liability is calculated by multiplying the embodied emissions of the goods by the applicable CBAM rate, minus any qualifying overseas carbon price already paid on those emissions. Businesses that have paid a genuine carbon price abroad are not charged twice.
The rate is sector-specific and set quarterly, based on the average UK ETS auction price for the preceding quarter and adjusted to reflect the proportion of emissions still covered by free allowances in that sector. Rates will therefore move with the carbon market rather than sitting fixed.
Importers can use independently verified data on the actual emissions embodied in their goods, or fall back on default values published by the government. Only direct emissions are captured from 2027; indirect emissions from electricity used in production are not expected to be brought into scope before 2029.
When Does UK CBAM Start, and What Are the Deadlines?
UK CBAM takes effect on 1 January 2027, but the first payment is not due until 31 May 2028. The compliance timeline is more staggered than the start date suggests, though the record-keeping obligation is immediate:
- 1 January 2027: CBAM enters into force. Record-keeping duties begin for all importers of CBAM goods, whether or not they ultimately register.
- Records retained for six years: This applies from the first affected import.
- First accounting period: 1 January to 31 December 2027, reported as a single annual return.
- 31 May 2028: Deadline for the first return and first payment.
- From 2028 onward: Reporting moves to quarterly accounting periods.
Registered businesses must file a return even where no tax is ultimately due.
Challenges and Open Questions
The policy is not yet fully specified, and that is the principal difficulty for businesses trying to plan. As of August 2026, HMRC has confirmed the structure of the sector-specific default emissions values and quarterly rates but has not published the figures themselves. Importers can identify their exposure but cannot yet price it accurately.
Supplier data presents a second obstacle. Verified emissions data is the route to a lower liability where a supplier's production is genuinely cleaner than average, yet many overseas suppliers hold no such data and have little immediate incentive to produce it. Businesses defaulting to government values may pay more than their actual emissions warrant.
The UK has also skipped the transitional reporting phase the EU used to ease its own CBAM into effect. Both the UK and EU mechanisms begin charging from 1 January 2027, giving importers no grace period in which to test systems without financial consequence.
Industry concern is not hypothetical. Cement producer Breedon has publicly warned that unclear carbon border rules pose a risk to the UK cement industry, and construction sector buyers are watching how far the cost passes down the chain.
Practical Steps for SMEs Before January 2027
Preparation is largely a data exercise, and it can begin now:
- Audit import records: Review the last 12 months of imports against the five covered sectors and their commodity codes. Many businesses discover exposure they did not expect in fabricated or semi-finished products.
- Confirm who holds the liability: Check whose name appears on customs declarations. If an agent is used, confirm in writing where responsibility for CBAM sits.
- Approach suppliers early: Request verified emissions data for affected goods well ahead of 2027. Suppliers who can provide it become more valuable; those who cannot may cost more to buy from.
- Model the cost: Even with default values unpublished, indicative modelling against current UK ETS prices gives a workable planning range.
- Build internal understanding: Someone in the organisation needs to understand emissions accounting well enough to interrogate supplier data and challenge default values.
The Path Forward
CBAM represents a shift in how carbon costs reach smaller businesses. Where previous carbon policy applied mainly to large emitters, this mechanism reaches any importer crossing a modest financial threshold, regardless of size or sector. The £50,000 exemption protects the smallest importers, but a builders' merchant, fabricator or manufacturing SME buying steel or aluminium abroad will cross it comfortably.
The businesses that fare best will be those treating the next eighteen months as preparation rather than waiting for the first return in May 2028. Understanding embodied emissions in a supply chain is useful well beyond CBAM compliance — the same data underpins Scope 3 reporting, customer disclosure requests and procurement decisions. Building that capability now converts a compliance obligation into commercial insight.
Frequently Asked Questions
Does UK CBAM apply to businesses importing less than £50,000 of goods?
No charge applies below the threshold, but record-keeping still does. Importers below £50,000 over a rolling 12-month period are exempt from registration and payment, though records of CBAM goods must be kept from 1 January 2027 and retained for six years. The threshold is reassessed on the first day of every month, so a business can cross it partway through a year.
Is a customs broker or freight forwarder responsible for UK CBAM?
No. Liability rests with the liable person, generally whoever is named on the customs declaration, which is usually the importer itself. Appointing an agent to handle declarations does not transfer registration, reporting or payment duties.
How does UK CBAM differ from the EU version?
The UK has no transitional reporting phase. The EU ran a reporting-only period before charging began, whereas the UK moves straight to a chargeable regime on 1 January 2027. Businesses importing into both markets will face two separate registrations and two sets of returns.
What records do importers need to keep for UK CBAM?
Records covering the CBAM goods imported, the emissions embodied in them, and any overseas carbon price already paid on those emissions. These must be retained for six years, and the duty applies whether or not the business ultimately registers.
Does UK CBAM cover indirect emissions from electricity?
Not initially. Only direct emissions from the production process are captured from 2027. Indirect emissions from purchased electricity are not expected to come into scope before 2029, though importers should plan for the scope to widen over time.
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