UK HMRC Issues Guidance on CBAM Record-Keeping Requirements and Penalties
16 juli 2026HM Revenue & Customs (HMRC) has published detailed guidance on the mandatory 6-year record-keeping requirements and associated penalties for UK CBAM importers ahead of the 2027 launch.
HM Revenue & Customs (HMRC) has released new guidance outlining the mandatory record-keeping requirements for importers of Carbon Border Adjustment Mechanism (CBAM) goods into the UK. With the tax coming into effect on January 1, 2027, businesses must ensure they establish compliant record-keeping procedures to track imported goods and avoid statutory penalties.
Key Retention Rules and Penalties
Importers must keep all relevant CBAM records in written or electronic form for 6 years from whichever date is latest: the date they were created or the end of the accounting period to which they relate.
Penalty Warning: Failure to maintain proper records for CBAM may result in a fixed penalty of £500 from HMRC. Separate penalties may also apply if an importer fails to provide requested documents or information to tax authorities.
Mandatory Import & Goods Records
Starting January 1, 2027, anyone importing CBAM goods into the UK must maintain detailed records containing:
8-digit commodity code and full product description.
Tax point date (when the goods first entered the UK or cleared customs).
Value and net weight (excluding packaging).
Evidence of any exemptions claimed.
When completing CBAM returns, importers must also maintain proof of origin, customs documentation (such as import declarations, bills of lading, or records of movement), and the specific quarter in which the goods passed the tax point.
Actual Emissions vs. Default Values
If an importer chooses to report actual emissions rather than default values, they must retain verifiable evidence from their supplier—such as a verification report or summary—for 6 years.
Default Values: Importers must use a default emissions value if actual emissions data is unavailable or unverified.
Upcoming Guidance: HMRC announced that official default emissions values, as well as detailed monitoring and verification rules, will be published later in 2026.
Weight Calculation & Net Mass Rules
Weight records must show the net mass in kilograms at the time of import into the UK, up to 6 decimal places.
Fraction of a Unit (kg) | Rounding Rule |
0.001 to 0.499 | Round down to the nearest kg |
0.500 to 0.999 | Round up to the nearest kg |
Less than 1 kg | Format as
followed by up to 6 decimals (e.g.,
for 123g) |
Additionally, when CBAM registration opens by January 1, 2028, importers will need to provide estimated weights for the next 12 months across each covered sector (aluminium, cement, fertiliser, hydrogen, iron and steel) and keep records of how those estimates were calculated.
Tax Relief, Repayments, and Exemptions
Importers must maintain specific verification and transactional records for tax adjustments and exemptions:
Carbon Price Relief: If claiming relief for carbon costs already paid under an overseas qualifying scheme, importers must retain a completed carbon price verification form, exchange rate details used for conversion to GBP, and verified effective price calculations.
Repayment Claims: Records of repayment claims submitted to HMRC must be kept for 6 years from the date the claim is sent. HMRC will only repay overpaid CBAM for the 3 years preceding the claim.
Exemptions: Importers claiming exemptions must retain supporting proof for private use items, UK origin goods, Returned Goods Relief (re-imported within 3 years unaltered), or goods under temporary admission with full relief.