A new tax with a £50,000 threshold sounds like something for the big importers to worry about. It isn't. Invest NI's Green Economy team used its 24 September feature to flag the UK's new Carbon Border Adjustment Mechanism (CBAM) to Northern Ireland manufacturers, and buried in HMRC's own policy detail is the figure that should get a smaller business's attention: £50,000 of imports in a rolling year is enough to trigger a duty to register, based purely on the value of the goods you import, whatever the size of the business buying them.
That threshold catches a lot more than steelworks and cement plants. Anyone in Northern Ireland who regularly imports structural steel, cement, fertiliser, aluminium or hydrogen-linked goods from outside the UK, for a construction job, a fabrication run, or a supply chain that happens to route through a non-UK producer, needs to know this is coming. £50,000 a year is not a high bar for a working construction or engineering business.
What UK CBAM actually is
This is the UK's own scheme, separate from the EU's carbon border tax, which already applies to EU imports. It's confirmed in HM Revenue & Customs' CBAM policy summary, updated 9 September 2026, following primary legislation in the Finance Act 2026. It commences on 1 January 2027 and applies, in HMRC's own words, "across the whole of the UK, including Northern Ireland." It places a carbon price on the emissions embodied in imports in five sectors: aluminium, cement, fertiliser, hydrogen, and iron and steel, sectors that map directly onto Northern Ireland's construction and manufacturing base.
The Northern Ireland twist
HMRC's policy summary sets out one rule that exists only because of Northern Ireland's position under the Windsor Framework: goods that leave Northern Ireland to be processed in the EU, and then return, get a specific carve-out. Where a "Union good" is exported from Northern Ireland into the EU and reimported into the UK, there's no CBAM liability, provided it comes back within three years of export and in the same state it left in. That's a genuinely Northern Ireland-only provision. A business in Leeds or Cardiff sending goods for EU processing has no equivalent relief, because its goods are not leaving from Northern Ireland in the first place.
The number that matters: £50,000
Registration isn't optional once you cross the threshold, and HMRC applies two separate tests, either of which can trigger it. The backward-looking test runs on the first day of every month: look back over the preceding 12 months, and if the value of CBAM goods you've imported meets or exceeds £50,000, your liability to register starts that day. The forward-looking test runs continuously: on any given day, if you expect the value of CBAM goods you'll import over the next 30 days to reach £50,000, your liability starts then, before the goods have even landed.
Two illustrative examples show how easily ordinary Northern Ireland trade reaches that line.
| Illustrative Northern Ireland business | CBAM goods imported | Test tripped |
|---|---|---|
| Mid-Ulster steel fabricator, around £4,500 a month of structural steel from outside the UK | ~£54,000 over a rolling 12 months | Backward-looking test, the month the 12-month total first clears £50,000 |
| Antrim civils contractor, one imported cement shipment for a single contract | £62,000, landing within 3 weeks of the order | Forward-looking test, the day the order is placed |
Neither of those is the kind of heavy industrial importer CBAM sounds like it should be aimed at. One is a steady monthly habit; the other is a single order for one job. Both create a registration duty under HMRC's rules as they currently stand.
What it means in practice
Once the liability test is met, the clock starts. Ordinarily a liable person has 30 days to register with HMRC from the day they become liable, but HMRC has built in a concession for the first year: anyone who becomes liable during the 2027 calendar year has until 31 January 2028 to register, regardless of when in 2027 the threshold was crossed. The first CBAM accounting period runs the full 12 months from 1 January to 31 December 2027, with the first return and payment due 31 May 2028. From 2028 onward, accounting periods move to a quarterly cycle with a tighter payment window. Registration itself asks for the basics: name, business address, EORI number, VAT number if you have one, plus the estimated weight of CBAM goods you expect to import over the coming 12 months in each sector.
The harder part isn't the registration form, it's the emissions data behind each return. A CBAM return needs the emissions intensity of the imported goods, and the preferred source is verified data direct from the producer, meaning Northern Ireland importers need to be asking their non-UK suppliers now, months ahead of December 2026, whether they can provide it. Invest NI's own advice to manufacturers is to start strengthening carbon reporting today. Default values won't appear until closer to launch, so supplier data is the only route available in the meantime.
What to do this week
Pull your last 12 months of import records now and check the total value of anything in the aluminium, cement, fertiliser, hydrogen, or iron and steel sectors against the £50,000 threshold, using HMRC's CBAM policy summary as the reference for what's actually in scope. If you're placing a large one-off order for imported materials on a specific contract, check its value against £50,000 before you place it, since the forward-looking test can trigger registration the day you commit to the order, weeks before the goods arrive. Start the conversation with your non-UK suppliers about emissions data now — HMRC's default values are not expected until much closer to the 2027 start.
This sits alongside the switch to the new Trader Support Service platform we covered a few weeks ago. CBAM is a tax on imported goods, a different mechanism entirely from the Trader Support Service's job of tracking GB-to-NI movements. The discipline it demands is familiar all the same: know what you're importing, keep the records, and register before HMRC comes looking.
What's still uncertain, and when we'll know
The actual cost of a CBAM liability isn't fixed yet. HMRC will publish the CBAM rate per sector at the start of each quarter from January 2027, calculated against the UK Emissions Trading Scheme carbon price; an illustrative example rate is promised for autumn 2026, but nothing published so far puts a number on what a tonne of imported steel or cement will actually cost under CBAM. Default emissions values, for businesses that can't get verified data from suppliers, are also still to come, due in advance of the January 2027 start with no firmer date set. Full step-by-step registration guidance is likewise still to be published on GOV.UK. What is fixed: the 1 January 2027 start date, the £50,000 threshold, and the sectors in scope, all confirmed in HMRC's policy summary updated 9 September 2026.
Working out whether your business is already close to that £50,000 line, and what a registration duty would actually mean for your paperwork, is exactly the kind of thing our tax planning service is built to check before it becomes urgent, and our management accounts service keeps import spend visible enough, month by month, that a threshold like this doesn't arrive as a surprise.