CBAM Lands in 2027. The Baseline Doesn’t.

Northern European hot-rolled coil climbed €40 a tonne in the first eight weeks of 2026 as the EU Carbon Border Adjustment Mechanism went definitive. The UK version lands 1 January 2027. Most businesses have no baseline to model it against.

Platts assessed northern European hot-rolled coil at €660/tonne ex-works Ruhr on 24 February 2026, up €40 since the start of the year and the highest level since April 2024 (S&P Global). The reason is a tax. The EU Carbon Border Adjustment Mechanism entered its definitive phase on 1 January 2026 and the cost of embedded carbon in imported steel started landing on invoices the same month. The first official EU CBAM certificate price was set at €75.36/tCO2 for Q1 2026 (EUROMETAL).

The UK version lands on 1 January 2027. This piece sets out what it is, how the UK and EU designs differ, who it reaches, and what a defensible readiness position looks like before Q4 2026.

What CBAM Is

A Carbon Border Adjustment Mechanism is a tariff on the embedded carbon in imported goods. It closes the carbon leakage loophole: when a country prices domestic emissions through an ETS but lets imports in free of carbon cost, production moves offshore. CBAM charges imports the same effective carbon price domestic producers already pay.

The UK design covers aluminium, cement, fertilisers, hydrogen and iron & steel. A £50,000 annual threshold applies across all in-scope commodities combined, which HMRC estimates removes over 80% of otherwise affected importers (around 70% of those are SMEs). HMRC sets the rate quarterly, reflecting the average UK ETS price over the prior quarter. The illustrative rate is due Autumn 2026. Glass and ceramics are excluded. Indirect (Scope 2) emissions are deferred to 2029 (GOV.UK Policy Summary).

Where the UK and EU Diverge

The divergences are architectural, not cosmetic. They decide who is caught, where, and when. Businesses operating across both borders need to hold two sets of rules at once.

The UK chose a money threshold. The EU chose a cumulative mass threshold. The EU simplification adopted in October 2025 exempts any importer bringing in 50 tonnes or less of CBAM goods per year, removing roughly 182,000 importers while still covering over 99% of in-scope emissions (European Commission). The same supply chain can be caught on one side of the Channel and exempt on the other. This is not a rounding error. It changes where the obligation sits in a cross-border supply chain.

So What. Who Is Affected

CBAM reaches further than the list of five sectors suggests. Four groups should be running the numbers now:

1. Direct importers of the five in-scope commodities. At current UK steel prices, £50,000 is roughly 20 to 30 tonnes of steel or 15 tonnes of primary aluminium per year. Most capital procurement programmes cross it.
2. Construction and housebuilders. Even if you are not the direct importer, suppliers pass the cost through. Contracts written in 2026 without CBAM pass-through language get rebased when the first HMRC quarterly rate drops in 2027.
3. Social housing associations. Reinforcement steel, aluminium cladding and cement sit at the top of every retrofit and new build cost plan, and all three are in scope from day one. Most providers have never built a Scope 3 baseline. The exposure cannot be priced until that baseline exists.
4. Climate disclosure reporters under TCFD, AASB S2 and ISSB. CBAM is a direct line between a tariff on the invoice and a climate-related financial risk that has to be disclosed. Boards that signed a 2030 target without modelling CBAM will be asked for updated numbers.

Most businesses do not have a baseline. Not a CBAM baseline. Any baseline. ESG decks, a Scope 1 number from utility bills, a rough Scope 2 estimate. Scope 3 is a blank page. Without that page filled in, the exposure cannot be modelled.

How SustainTrue Helps

The gap is management information, not regulation. The CBAM obligation is clear. The baseline underneath it is not. That is what we build. A defensible CBAM readiness position has five elements. SustainQ gives teams all five in one platform:

• Baseline. Validated Scope 1, 2 and 3 inventory with commodity-level detail for the five CBAM sectors, mapped to GHG Protocol and ready for HMRC declaration logic.
• Commodity mapping. Procurement spend matched against in-scope commodity codes (aluminium 7601, cement 2523, fertilisers 3102, hydrogen 2804, iron and steel 7208), with country of origin and supplier breakdown.
• Exposure modelling. Scenario runs against the illustrative rate (Autumn 2026) and HMRC's quarterly rate trajectory, so boards can price the hit before it lands.
• Disclosure integration. CBAM numbers flow into Scope 3, transition plan and climate-related financial risk reporting. One baseline, four deliverables.
• Contract review. Procurement contracts checked for pass-through clauses before Q4 2026, so you are not absorbing a rebased cost you never priced.

SustainQ

How teams are getting ready for CBAM

✓Validated Scope 1, 2 and 3 baseline with commodity-level detail across procurement

✓Embedded carbon tracking by supplier, commodity code and country of origin

✓Scenario modelling for CBAM exposure under HMRC's illustrative and quarterly rate trajectories

✓Integrated disclosure across CBAM declarations, transition plans and climate-related financial reporting

Book a Democontact@sustaintrue.com

Sources

• HMRC, Carbon Border Adjustment Mechanism Policy Summary
• HMRC, Factsheet: Carbon border adjustment mechanism
• HM Treasury, Government response to the policy design consultation (PDF)
• House of Commons Library, Carbon Border Adjustment Mechanism briefing
• European Commission, Carbon Border Adjustment Mechanism
• European Commission, CBAM Simplification Regulation (October 2025)
• ICAP, UK CBAM introduction from 2027
• techUK, Government confirms introduction of a UK CBAM in 2027
• S&P Global Platts, European domestic flat steel prices reach highest levels since 2024
• EUROMETAL, CBAM certificate price for Q1 2026 = €75.36