Britain’s tax authority, HM Revenue & Customs (HMRC), updated its official policy summary on 2 November, clarifying how importers must calculate Carbon Price Relief under the forthcoming Carbon Border Adjustment Mechanism (CBAM). The UK CBAM enters into force on 1 January 2027 and covers selected imports of steel, aluminium, cement, fertilisers and hydrogen. Carbon Price Relief allows qualifying foreign carbon costs to reduce an importer’s UK CBAM liabilities.
Under the guidance, importers must use consistent emissions when calculating the carbon charge and determining relief. They must first establish the effective qualifying foreign carbon price after accounting for compensation, rebates and other adjustments, then apply it to the corresponding embedded emissions. The amount eligible for relief can therefore differ from the headline rate of a national carbon tax or emissions-trading scheme, particularly where free allowances or compensation lower actual carbon payments.
Where production involves multiple installations, precursor materials or different carbon-pricing arrangements, the related emissions and payments may need to be treated separately, HMRC’s summary says. The rules do not permit an importer to multiply total product emissions by a scheme’s headline rate to calculate a deduction. Instead, the calculation must connect the relevant emissions to the qualifying carbon cost incurred.
Evidence requirements for exporters
Britain’s provisional list of qualifying schemes includes the Serbia Carbon Tax and the Montenegro Emissions Trading Scheme. Their inclusion does not automatically qualify every manufacturer operating in either country for relief. The emissions must have incurred a qualifying carbon cost, and importers must hold sufficient supporting documentation. HMRC’s guidance also requires independent verification of carbon-price evidence used for a claim.
For Serbian steel and aluminium suppliers, the rules link domestic tax records and production emissions to the competitiveness of exports to Britain. Montenegrin industrial producers face similar requirements when emissions covered by their domestic scheme can be linked to specific exported goods. British customers need product-specific data to calculate the effective carbon price; generic certificates showing participation in an emissions scheme are not enough.
Banks financing industrial exporters should not treat a potential deduction as a secure commercial benefit until eligibility and documentation have been established. HMRC’s update clarifies calculation rules but introduces no new exemption and does not postpone the January 2027 start date.