Can a UK importer correct a CBAM return later?
Yes, within 3 years of the end of the accounting period the return covers. An error that caused an overpayment can be repaid, but not amounts paid more than 3 years before the claim. One thing cannot be fixed: a return filed with default values cannot later be amended with actual emissions data.
The windows
- Amendment: within 3 years of the end of the accounting period.
- Repayment of an overpayment: allowed, except for amounts paid more than 3 years before the repayment claim.
- Evidence: the importer keeps records that support the correction, and HMRC may ask for them first.
The default value trap
HMRC says that if a return uses default values, it cannot be amended later with actual emissions data. A lower verified figure that arrives after filing is lost for those goods. Your verification needs to be finished before your buyer files.
What this means for an Indian plant
For goods imported in 2027, the return is due by 31 May 2028, and HMRC's timeline has your verification report reaching your buyer before then. Agree a date for your verified figure with your buyer early, or expect them to file on defaults.
The 2027 return
- Accounting period: 1 January to 31 December 2027. Return due 31 May 2028.
- Amendment window: until 31 December 2030.
- Filed on defaults in May 2028; your verified figure arrives in July 2028: it cannot replace the defaults.
What Senseible does here
Senseible builds your per-product figure from invoices as the year runs, so it can go to a verifier soon after year end. We build the figure from your records and check every figure in-house; for the UK it must then be verified by a verifier accredited for UK CBAM. Have your own verifier? Send it to them.
Sources: HMRC, Carbon Border Adjustment Mechanism (CBAM): Policy summary (updated 2 November 2026), HMRC, UK CBAM iron and steel default values, HMRC, UK CBAM monitoring, reporting and verification technical guidance (October 2026)
Last reviewed 2026-11-03.