CBAM Pulse
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HMRC clarifies net-mass records for UK CBAM

HMRC updated its UK CBAM records guidance on 3 November 2026 to explain how to record the net mass of imported goods in kilograms. The guidance specifies up to six decimal places, explains entries below one kilogram, and permits rounding in the stated cases above one kilogram. This is a UK record-keeping clarification, not a change to EU CBAM thresholds or calculator assumptions.

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What changed

  • HMRC's dated change history says the section 'Weight of goods records you should keep' was updated on 3 November 2026 to explain net-mass entry. The page was originally published on 16 July; this briefing reports the later clarification.
  • The guidance describes net mass as the goods' weight excluding packaging, at the time of import into the UK. It says to enter that mass in kilograms, up to six decimal places, following the named CDS goods-identification instructions.
  • For a net mass greater than one kilogram that includes a fractional kilogram, the guidance says it may be rounded to the nearest kilogram. This is not a statement that every imported quantity must be rounded.
  • For net mass below one kilogram, the guidance describes an entry beginning '0.' followed by up to six decimal places, discarding trailing zeros. Open HMRC's page for its examples and complete record-keeping context.
  • This guidance belongs to the separate UK regime. It does not amend the EU's mass-based threshold test or CBAM Pulse's goods data, thresholds, calculations or assumptions.

Who may be affected

Businesses preparing records for imports within UK CBAM, their customs agents and advisers. This briefing does not determine whether any particular goods or importer are in scope or prescribe a filing on their behalf.

Official sources

Summary prepared by CBAM Pulse from the official sources linked above. It is informational only and not legal, tax, or customs advice. In case of any difference, the official text prevails.

Explore this topic

  • UK CBAM: records and preparation

    Read the separate UK regime's existing guide alongside HMRC's complete records guidance; no EU threshold or calculation rule changes here.