UK CBAM Record Keeping: What You Must Keep and For How Long

HMRC requires all UK CBAM declarants to maintain a complete set of records supporting every figure declared in every CBAM return. The obligation runs for six years from the filing date of each return. These records must be held in a format that HMRC can inspect on request, and you must be able to produce them within a reasonable timeframe.

The record-keeping requirement covers import ledgers, customs declarations, supplier emissions data, calculation methodologies, correspondence with suppliers, evidence of carbon price relief claims, and copies of every CBAM return filed. Each record must be linked to the specific return and shipment it supports.

For supplier emissions data, you must retain the original documents received from your supplier, not just a summary or transcription. If the supplier provided figures in an email, keep the email. If they uploaded a PDF certificate, keep the PDF. HMRC expects to see the source documents, not your working notes.

Oremly's evidence store does this automatically. Every document uploaded by you or your supplier is checksummed and stored with an append-only audit log. Every figure in every return is linked to its source document, so you can produce the complete evidence package in seconds.

HMRC does not prescribe a specific format for CBAM records, but the records must be legible, complete, and capable of being produced in a format HMRC can inspect. Digital records are acceptable and encouraged. Paper records must be organised and indexed.

If you maintain digital records, HMRC expects them to be backed up and not stored on a single device or in a single location. Loss of records due to equipment failure or data corruption is not accepted as a defence for non-production.

Records must be produced in English, or accompanied by a certified English translation. HMRC may request records in a specific format for inspection, and you must comply within a reasonable timeframe. HMRC typically allows 30 days for record production but may request urgent production in cases of suspected non-compliance.

The six-year retention period runs from the filing date of each CBAM return. For the first annual return (2027, filed by 31 January 2028), records must be retained until at least 31 January 2034. For the first quarterly returns (from 2030), the six-year clock starts from each quarterly filing date.

This means records for different reporting periods will have different retention end dates. As your CBAM history grows, you will hold records spanning multiple years, with the oldest records becoming eligible for destruction after their respective six-year periods expire.

The retention period does not reset if you are audited. If HMRC opens an audit in year four, you must retain the records for the full six years regardless of when the audit concludes. If litigation or a penalty dispute is ongoing at the six-year mark, you should retain records until the matter is resolved.

Failing to maintain adequate CBAM records or failing to produce them on request carries a fixed penalty of up to £500. If the failure is part of a broader pattern of non-compliance, HMRC may escalate to percentage-based penalties on the underpaid liability.

In practice, the record-keeping penalty is most commonly triggered when HMRC opens an audit and the declarant cannot produce supporting evidence. The message to importers is clear: if you cannot prove your figures, you cannot defend your return.

Oremly's audit-ready evidence store eliminates this risk. Every document is automatically retained, indexed, and linked to the correct return. When HMRC asks, you produce the complete package with one click.