What weight goes on a UK CBAM return for our goods?
The net mass in kilograms, without packaging, at the time of import. Above 1 kg it is rounded to the nearest kilogram, with 0.5 kg or more rounding up. HMRC accepts import declarations, commercial invoices, packing lists, bills of lading or carrier weight records as evidence.
What counts
- Net mass of the CBAM good only: no pallets, crates, drums, strapping or other packing.
- Measured at the time the goods enter the UK.
- Reported in kilograms; HMRC converts to tonnes to work out embodied emissions.
Rounding
- More than 1 kg with a fraction: 0.499999 kg or less rounds down, 0.5 kg or more rounds up.
- Less than 1 kg: written as 0. followed by up to 6 decimals, for example 0.123 kg for 123 grams.
Why your invoice matters
The importer must keep evidence of how it arrived at the weight, and may take it from documents you supply. If the weight looks wrong or records are missing, HMRC can set the weight itself by estimate or by comparison with similar goods. Show net and gross weight separately on every invoice and packing list for UK shipments.
Worked example: a fastener shipment
- Gross weight on the bill of lading: 20,640 kg.
- Pallets and cartons: 1,180 kg.
- Net mass reported: 20,640 minus 1,180 = 19,460 kg.
- HMRC uses 19.46 tonnes times the emissions intensity.
What Senseible does here
Senseible reads quantities from your sales and freight documents, so the tonnes behind an emissions figure match the tonnes you shipped. 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, Keeping records for CBAM, HMRC, Carbon Border Adjustment Mechanism (CBAM): Policy summary (updated 2 November 2026)
Last reviewed 2026-11-02.