On 16 October 2026, HM Revenue & Customs published the technical guidance for monitoring, verifying and reporting emissions under the UK Carbon Border Adjustment Mechanism. It runs to 313 pages. Most exporters will never read it, and they do not need to. But one fact buried in the first chapters deserves the attention of every producer selling into the UK: emissions data from the 2026 calendar year can already be used for goods imported in 2027. The clock did not start in January. It started ten months ago.
What the UK actually published
From 1 January 2027, the UK CBAM applies to imports of aluminium, cement, fertiliser, hydrogen and iron and steel. The legal duty sits with the UK importer, the “liable person”, who registers once their CBAM goods reach £50,000 in value over a 12-month period. The importer either reports actual, verified emissions data or falls back on default values.
The new document is the operating manual for that choice. It tells an overseas installation how to define its production processes, which parameters to monitor, how to build a monitoring plan, how to keep records, and what an independent verifier will check. The framework is closely aligned with the UK Emissions Trading Scheme, so any verifier or consultant familiar with UK ETS will recognise the structure.
HMRC is still inviting technical feedback until 13 November 2026 and may refine the document before the start date. The architecture, though, is fixed: monitor, verify, hand the verification report to your customer.
You will never file anything with HMRC. Your customer will.
One design decision matters commercially. The operator, the producing installation outside the UK, reports nothing to HMRC. Only the importer files a CBAM tax return. What the operator supplies is the evidence pack: a verification report, or a summary of it, covering the emissions intensity of the goods.
That makes UK CBAM, like the EU version, a commercial conversation rather than a customs formality. Your UK customer decides whether to use your actual data or the default values. If your data is missing, late or unverifiable, the default values apply, and the cost lands in your customer’s calculation. Suppliers who make their customers’ returns cheaper and safer will keep the business. Suppliers who create work will be priced accordingly.
The UK importer carries the legal duty, but the operator carries the data. Whoever delivers clean, verified numbers becomes the easy supplier to keep.
The timeline most exporters have not noticed
The monitoring period under UK CBAM is one calendar year. For goods imported during 2027, the importer can use verified emissions intensity from the 2026 or 2027 monitoring period, or from the period in which the goods were produced. The first return, covering 2027 imports, is due by 31 May 2028. From 2028, returns become quarterly.
Read that again from the operator’s side. An installation that monitored its emissions properly through 2026 can hand its UK customers a verified 2026 dataset for their very first return. An installation that starts thinking about this in January 2027 has already lost a full year of usable data and will spend its first CBAM year on default values.
Verification reports also have a shelf life. From 2028, the report used for an import cannot be more than two calendar years old. Monitoring is not a project with an end date. It is a permanent discipline, like bookkeeping.
Where the UK rulebook differs from the EU one
Companies already preparing for EU CBAM should not assume one data pack covers both markets. Three differences stand out in the guidance.
- 1.
Direct emissions only
UK CBAM covers direct emissions from production plus emissions embodied in relevant precursor goods. Indirect emissions from electricity use are not included. The gases in scope are CO2, nitrous oxide and the two perfluorocarbons CF4 and C2F6, converted to CO2-equivalent for reporting.
- 2.
A tax return, not certificates
The UK importer files a CBAM tax return with HMRC and pays a liability. There is no certificate market to navigate, no weekly price average, no surrender deadline. The mechanics are closer to a customs duty calculation than to the EU’s ETS-linked system.
- 3.
A value threshold, not a mass threshold
UK registration turns on £50,000 of CBAM goods over 12 months, where the EU applies a 50-tonne annual mass threshold. A niche, high-value exporter can be in scope in the UK while sitting below the EU threshold, and the reverse is equally possible.
The good news: the underlying plant data is largely the same. Production routes, activity levels, fuel and material inputs, precursor emissions. An installation that builds one solid monitoring system can serve both markets, with two different report formats on top. We covered the strategic side of running both rulebooks in an earlier piece, linked below.
What an exporter into the UK should do now
- 1.
Check your commodity codes
Compare your products against Schedule 16 of the Finance Act 2026 or Annex VII of the guidance. Remember that the same code can cover both a finished good you sell and a precursor you buy.
- 2.
Ask your UK customers one question
Will they use actual data or default values for your goods? Their answer tells you exactly how much your data is worth to them, and it starts the conversation on your terms.
- 3.
Treat 2026 as your first monitoring year
If your records for this year are incomplete, close the gaps now while the year is still open. Meter readings, fuel purchases, production volumes, precursor deliveries. Reconstructing a year afterwards is far more expensive than recording it.
- 4.
Write the monitoring plan before you need it
The guidance expects a documented plan: system boundaries, parameters, methodologies, data sources, control measures. Verifiers will ask for it first.
- 5.
Line up a verifier early
Independent verification is mandatory for actual data, and accredited capacity will be tight in the first cycle. The first reports for 2027 imports must reach your customers before 31 May 2028.
Find out where you stand before your customer asks
Our free CBAM Readiness Assessment shows which of your products fall under the UK and EU scopes, what default values would mean for your customers, and where your data gaps sit. It takes about 15 minutes and ends with a review by our CBAM team.
Start the free CBAM Readiness AssessmentSources and editorial references
- HM Revenue & Customs, “Carbon Border Adjustment Mechanism (CBAM): technical guidance for monitoring, verifying and reporting emissions”, published 16 October 2026 (gov.uk)
- Finance Act 2026, Schedule 16 (CBAM commodity codes)
- HMRC CBAM guidance collection (gov.uk)
This article is our own analysis of the published guidance. The guidance itself is subject to a feedback window until 13 November 2026 and may be updated before 1 January 2027; check the current version before making decisions for your installation.
Jessica Boyd
Jessica Boyd is Partner and Senior Consultant at wis.dom|bridge™. She advises companies on cross-border operations, CBAM readiness and the practical structures needed to keep trade compliant and commercially viable.
