Steel importers' 2027 cost stack: the 50% tariff, halved quotas and CBAM together

Two trade measures are landing on the same importers six months apart, designed by different departments for different reasons, and almost nobody is modelling them together. If you import steel — coil, bar, tube, sections, or the bolts and fasteners that count too — your 2027 landed cost has a new stack on top of the mill price, and the two layers behave differently enough that the combined answer isn't intuitive.

Layer one: the steel trade measure (live since 1 July 2026)

The old steel safeguard, with its 25% additional duty, ended on 30 June 2026. From 1 July 2026 it was replaced by a tighter regime, set out on the UK Integrated Online Tariff:

• Quotas cut by 51% against the previous safeguard volumes, across 20 steel product categories — products that can be made in the UK.
• Imports above the quota pay a 50% tariff on customs value.
• Duty-free quota is administered by HMRC first-come, first-served, in quarterly tranches; unused quarterly quota rolls into the next quarter but not into the next quota year.
• A transitional exemption spared goods under contract before 14 March 2026 from the out-of-quota duty between July and September 2026 — that window closes at the end of this month.

The practical shape of this is a race: early in each quarter, quota is available; once your category's tranche is exhausted, the marginal tonne costs half again as much. Importers who ship late in a quarter, or in a popular category, meet the 50% tariff more often than the headline suggests.

Layer two: UK CBAM (from 1 January 2027)

The carbon border charge works on a completely different basis. It is not a percentage of value; it is pounds per tonne of embodied carbon: the tonnes of CO₂e in the steel, multiplied by a quarterly government-set rate derived from UK ETS auction prices, less any carbon price already paid at origin. The rules are settled law (Finance Act 2026 and the rate regulations made in July); the numbers are not yet — HMRC's default emissions values and the first rate are still to be published, with an illustrative rate promised this autumn.

To put a scale on it, using clearly-labelled scenario inputs: hot-rolled flat steel at roughly 2 tonnes of CO₂e per tonne (the EU's published default values, direct emissions only — a proxy for the UK's unpublished ones) and a rate of £49.25/tCO₂e (the real Q2 2026 UK ETS auction average with no free-allocation discount applied) gives a CBAM charge of around £99 per tonne of steel. UK ETS prices have risen since Q2 — the Q3 auctions to date are averaging higher — so if the eventual rate lands nearer the current market, that figure moves towards £115. Treat both as scenarios; treat the direction as real.

Why the two layers don't add the way you'd expect

The tariff scales with value; CBAM scales with carbon. A tonne of commodity rebar and a tonne of specialist alloy plate can attract wildly different 50% tariffs — but similar CBAM charges, because the carbon in a tonne of steel is set by how it was made, not what it sells for. Consequently:

• Cheap, heavy, commodity steel is hit proportionally hardest by CBAM. A £99/t carbon charge on £600/t rebar is a 16% cost increase; on £2,000/t plate it is 5%. The tariff is 50% of either.
• Being inside quota does nothing for CBAM. Quota status is about volume; CBAM is charged on every covered tonne from 1 January 2027, quota or no quota.
• Origin matters differently for each layer. For the tariff, what matters is category and timing within the quarter. For CBAM, what matters is how the steel was made and whether a carbon price was already paid where it was made — and HMRC's new official list of qualifying carbon pricing schemes now includes the EU ETS and China's national ETS, so steel from those origins may carry relief that steel from, say, an origin with no carbon pricing does not.

The upshot for anyone re-sourcing to manage the quota squeeze: a cheaper origin without carbon pricing can cost more in 2027 once CBAM lands on its typically higher carbon intensity, with no relief to offset it.

The three levers that actually move the total

1. Timing and category, for the tariff. Know your category's quarterly tranche and where you sit in the queue; a shipment that lands on the first working day of a quarter and one that lands in week eleven can differ by 50% of value.
2. Verified supplier emissions data, for CBAM. Default values are expected to be conservative — that is, high. Steel made in a modern electric-arc furnace can embody a fraction of the carbon of blast-furnace steel, but you only get that number on your return if the supplier's installation data is independently verified. Uncollected in 2027, unusable in 2028 — a return filed on defaults can never be amended to actual data later.
3. Carbon price relief, for CBAM. If the mill already paid a carbon price, the UK deducts the effective amount. It needs the official verification form completed during 2027; our relief guide explains why "listed" is not the same as "refunded".

What to do this quarter

• Pull your 2026 import ledger and run it through the liability preview — it prices every line at the labelled scenario rate, runs the £50,000 registration test, and ranks which suppliers to chase first. Ten seconds, nothing stored.
• Add the CBAM per-tonne scenario to whatever you use to model the tariff, and re-rank your origins on the combined number, not the tariff alone.
• Start the supplier conversation now — emissions data and carbon-price evidence in one ask — because both levers two and three are worth nothing if the paperwork isn't in hand during the year the liability arises.