What happened

edie and law firm Weightmans held an online webinar on the UK Carbon Border Adjustment Mechanism (CBAM), which is scheduled to begin on 1 January 2027. The session featured Weightmans partners Abhay Srivastava, who leads ESG, and Simon Colvin, head of the environment team.

The speakers said the UK system will operate as a tax administered by HM Revenue & Customs, rather than through the certificate model used by the EU. Its first phase covers aluminium, cement, fertilisers, hydrogen, iron and steel.

Liability will depend on the commodity codes of imported products and the value of relevant imports. Businesses must monitor whether those imports exceed £50,000; the threshold concerns import value, not the tax due.

Why it matters

Importers cannot transfer their legal CBAM responsibilities to customs agents, freight forwarders or other intermediaries. Companies buying through UK distributors may not be the liable importer, but could still face increased prices where CBAM costs are passed along the supply chain.

Participants discussed two routes for emissions calculations: government default figures or verified data on actual supplier emissions. Actual data may reduce liabilities for lower-emissions products, but requires supplier engagement, defined reporting boundaries and assurance from approved providers. About 67% of poll respondents identified supplier carbon information as a challenge.

Businesses should involve procurement, finance, legal and sustainability teams. They will need import registers, clear internal ownership, supplier data provisions in contracts and records supporting calculations, exemptions and carbon-price relief.

What's next

Businesses above the threshold during 2027 must register by 31 January 2028. Their first return and payment are due on 31 May 2028. From 2028, reporting and payments become quarterly, and registration will be required within 30 days of crossing the threshold.

The webinar advised regular, at least monthly, threshold reviews and early budgeting for possible cash-flow effects as annual and quarterly payments begin to overlap.