CBAM puts a carbon price on certain imported goods, including aluminium, cement, fertiliser, hydrogen, iron and steel. There is no reporting-only transition period before the charge begins. ¹

At first, that sounds like a tax issue. For importers, much of the work starts somewhere else: customs.

Before a business can understand what CBAM could cost, it needs to know exactly what it is importing. That means the right commodity codes, the value and weight of the goods, where they came from and how much carbon was produced when they were made.

That information may already sit across customs records, finance teams and overseas suppliers. CBAM brings it together, which is why waiting until the charge arrives could leave businesses with very little room to react.

The £50,000 registration threshold is a good example. Businesses must register when they meet or expect to meet £50,000 of CBAM imports. HMRC will look at both expected imports over the next 30 days and previous imports, so businesses need visibility over what is moving through their supply chain, not simply what they spend across a full year. ²

The emissions data behind those imports also matters.

Businesses can use actual emissions figures from the producer where the data meets HMRC’s requirements. If that information is not available, government-set default figures can be used instead.

The default gives importers a fallback, but it may not always give them the best result. If a producer operates with lower emissions than the government figure, using verified actual data could reduce the amount of carbon the charge is based on.

The challenge is getting that information in the first place.

Some suppliers will already have it. Others may never have been asked for it. Across a larger supply chain, finding the right data and checking that it can be used takes time. That makes supplier conversations one of the practical jobs’ worth starting now.

There is already pressure from the other direction too. The EU’s CBAM entered its definitive regime on 1 January 2026. The legal responsibility generally sits with the EU importer or its indirect customs representative, but UK suppliers may still be asked for the emissions information their customers need. ³

The UK and EU are working towards linking their Emissions Trading Systems. If that happens, it could create the conditions for goods moving between the two markets to be exempt from their respective CBAMs. ⁴ The UK Government has estimated that, without this kind of agreement, UK exporters could otherwise face up to £800 million in EU CBAM payments by 2030. ⁵

That agreement could change the picture, but it is not something businesses can rely on yet. Current UK guidance confirms that there are no CBAM exemptions in place through a linked emissions trading system today.

At Blaiklock, we believe customs planning belongs at the centre of CBAM preparation. Our recommendation is to act early: check which imports are affected, assess whether you could reach the registration threshold, speak to suppliers about emissions data and agree who will take responsibility internally.

Even businesses not directly responsible for CBAM could feel its impact through higher supplier prices. Understanding that exposure now will help inform budgets, contracts and future projects.

That is why CBAM should not sit in a box marked “carbon tax”.

Customs is becoming part of a much bigger commercial picture.

The businesses in the strongest position will be the ones that confident that they have the right information and know who owns the process.

Because by the time CBAM becomes a cost, the important work should already have been done.

Sources:

• HM Revenue & Customs — Carbon Border Adjustment Mechanism (CBAM): Policy Summary (updated July 2026).

• HM Revenue & Customs — Work out the date you’ll need to register for Carbon Border Adjustment Mechanism (CBAM) (July 2026).

• European Commission, Taxation and Customs Union — CBAM Definitive Regime (applicable from January 2026).

• UK Government — UK-EU Summit: Common Understanding, agreement to work towards linking the UK and EU Emissions Trading Systems and create the conditions for mutual CBAM exemptions (updated December 2025).

• UK Government — UK-EU Summit: Explainer, including the estimate that EU CBAM could have resulted in UK exporters paying up to £800 million into the EU budget by 2030 (updated December 2025).

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