The £50,000 UK CBAM threshold, explained

The £50,000 threshold decides whether UK CBAM is your problem at all — and it is widely misunderstood, usually in ways that flatter the answer. It is not "£50,000 a calendar year". It is not your total import bill. And it does not wait politely until year end to catch you. Here is how it actually works, straight from the legislation.

The two statutory tests

The Finance Act 2026 (Schedule 17) sets two tests. Triggering either one means you must register:

• The backward-looking test. On the first day of each month, look back over the preceding 12 months. If the covered goods you imported in that window total £50,000 or more in customs value, you have triggered registration that day. During 2027 the look-back reaches no further than 1 January 2027, so the window builds up through the year.
• The forward-looking test. On any day, if you expect to import £50,000 or more of covered goods within the next 30 days, you trigger immediately. This is the one that catches lumpy importers: a single large consignment puts you in scope the day you expect it, with no look-back needed.

If you meet both, your liability starts from the earlier of the two dates.

What counts towards £50,000

• Customs value — the same value used (or that would be used) to calculate customs duty on the goods. Not your invoice total with freight bolted on arbitrarily, and not your whole import spend.
• Covered goods only. Only goods whose commodity codes are on the statutory CBAM list count. A £2m importer whose CBAM-listed lines total £30,000 is under the threshold; a £60,000-a-year fastener importer is over it. Check which goods count here.
• Per legal entity. There is no group aggregation — each company is tested on its own imports. Before anyone gets ideas: the legislation contains specific anti-avoidance rules against artificially splitting a business to stay under the line.
• Some goods are disregarded, including UK-originating goods returning to the UK and goods under certain special customs procedures that are subsequently exported.

Worked examples

The steady importer. You import £10,000 of covered steel products every month from January 2027. Your cumulative total reaches £50,000 during May; on 1 June 2027 the first-day-of-month test finds £50,000 in the look-back window, and you have triggered. You must register by 31 January 2028 (the first-year easement — see below), and your first return, covering the whole of 2027, is due with payment by 31 May 2028.

The lumpy importer. You place one order a year: £60,000 of aluminium profiles landing in March 2027. On the day you expect that consignment to arrive within 30 days — realistically in February — the forward-looking test triggers. Same deadlines apply, but your in-scope date is months earlier than a cumulative reading would suggest.

The borderline case. You import £45,000 of covered goods a year. No trigger — this year. But the test re-runs on the first day of every month over a rolling window: a price increase, a new product line, or one opportunistic order can tip you over mid-year. Borderline businesses should track their covered-goods total monthly from January 2027 and be ready to register rather than discover the crossing in an audit.

Want this worked out for your numbers? The threshold checker runs the same logic in your browser.

Registration: when and how

Once triggered, registration is normally due within 30 days. For the first year there is an easement: anyone triggering at any point during 2027 has until 31 January 2028 to register with HMRC.

Registration will be through your Government Gateway account. Based on the draft regulations, expect to provide: business details and form, your EORI number, VAT number if registered, the date you triggered, the value of covered goods imported or expected, and your estimated weight of covered goods per sector for the next 12 months. That last item surprises people — weight, not just value, because the tax is charged per tonne of emissions. A tax agent can file returns for you later, but cannot register on your behalf.

HMRC has not yet opened registration or published its detailed guidance; late 2026 is the expected window. Joining our waitlist gets you a plain-English alert when it opens.

After you register

Registration itself costs nothing. What follows is the real work:

• Records per import line — 8-digit commodity code, weight, origin, customs value — retained for six years.
• Supplier emissions data — collected during the year it covers, or you take default values, and a return filed on defaults cannot later be amended to actuals.
• Returns and payment — the CY2027 return by 31 May 2028, then quarterly (with transitional deadlines of 31 July and 29 September 2028 for the first two quarters of 2028, settling to the last working day of the second month after each quarter).

If your imports genuinely stop or fall away, you can apply to deregister — HMRC can refuse if you have outstanding returns or amounts, or if it expects you to re-trigger within 12 months.

The traps, summarised

1. "We'll check at year end." The test runs monthly, and the forward test runs daily. Crossing dates matter.
2. "It's £50k of total imports." Covered goods only — but measured at customs value, which includes more than the bare product price.
3. "We're a group, we'll spread it around." Per-entity testing, with anti-avoidance aimed at exactly this.
4. "We're under it, so we can ignore CBAM." Borderline businesses wear the monitoring burden without the certainty. Track monthly.
5. "We'll sort the data out when we register in 2028." Registration is the trivial part. The 2027 emissions data you didn't collect in 2027 is gone; defaults fill the gap at whatever price the default table sets.

Sources

• Finance Act 2026, Schedule 17, paragraph 2 — the statutory tests
• HMRC: CBAM policy summary, April 2026 — threshold, registration and easement detail
• Draft CBAM (Administrative Provisions) Regulations 2026 — registration particulars and valuation