UK CBAM commences on 1 January 2027. It wants a field most mid-market ERPs do not hold reliably, and it wants it to six decimal places.
Legislated in Finance Act 2026. The first return is not due until 31 May 2028 — which is exactly why the data model has to exist inside purchasing months before the charge starts.
Who it binds
- Importers of aluminium, cement, fertiliser, hydrogen, and iron and steel into the UK.
- £50,000 registration threshold, tested two ways: forward-looking (expecting £50k or more in the next 30 days) and backward-looking (checked on the 1st of each month against the preceding 12 months). Imports before 1 January 2027 do not count.
- Glass and ceramics are excluded from 1 January 2027.
- Scope 2 / indirect emissions are deferred to 2029 at the earliest.
What it actually demands
- Eight-digit commodity code and description.
- Tax point date — UK entry or customs clearance.
- Value at import.
- Net mass in kilograms excluding packaging, to six decimal places.
- Proof of origin and exemption documentation.
- Supplier verification report and evidence the emissions data was verified, where using actual rather than default values.
- Carbon Price Relief: qualifying scheme evidence, verified effective carbon price, and the GBP conversion rates applied.
- Six-year retention. Fixed penalty of £500 for failing to keep records.
- By January 2028, estimated weights by sector plus the supporting calculation evidence.
Net mass excluding packaging at line level, against commodity code, is the field that decides this. Most ERPs hold gross weight, or hold net weight populated inconsistently by whoever set the item up, or hold it at item level when the requirement is per import line. Six years of retention means the lineage has to survive an ERP upgrade — so the data model and the estate remediation are the same conversation.
What it means for the estate
The integration point is between purchasing, customs and import records, and the general ledger. It is not a reporting layer bolted on at the end; it is a transaction design decision taken at goods receipt.
Reconciliation across purchase order, goods receipt, customs entry and the GL is the deliverable that makes the return defensible under enquiry. Without it you have a number you cannot explain.
First accounting period is the full 2027 calendar year, return and payment due 31 May 2028, then quarterly from 2028. Those liable during 2027 have until 31 January 2028 to register.
Caveat
Separately, EU CBAM has been in its definitive regime since 1 January 2026. If you export steel, aluminium, cement, fertiliser or hydrogen into the EU, your customer cannot file without installation-level embedded-emissions data from you. That is a different obligation with the same underlying dataset.
Primary sources
Run the exposure check — three minutes, free, and it will tell you which of the other 11 dates catch you as well and in what order they have to be done. Sequencing is most of the cost on these programmes.