# Which year's precursor data goes into a UK CBAM figure?

Canonical: https://senseible.earth/answers/uk-cbam-precursor-monitoring-period

One of two. HMRC lets the precursor's monitoring period be either the calendar year of the complex good you are reporting, or the calendar year in which the precursor itself was produced. Where precursors come from several installations and periods, the emissions are combined as a weighted average.

## The two choices

- Same year as your product: your 2027 bars use the billet supplier's 2027 verified figure.
- Year the precursor was made: billet made in late 2026 and rolled in 2027 can carry the supplier's 2026 figure.

## What to collect from each supplier

- The precursor's emissions intensity, averaged over its most recent monitoring period, in tCO2e per tonne.
- The start and end dates of that monitoring period.
- The installation that made it: identifier if any, UN/LOCODE, address and coordinates.
- The production route and the tonnes you used in each production process.

## When the dates matter to your verifier

If you use precursors you do not make, HMRC's guidance says you give your verifier their emission intensities and verification reports and, where relevant, evidence of when they were produced. Keep heat numbers or dispatch dates that tie each lot to a production year.

## If a supplier has no verified figure

For any quantity with incomplete or inconclusive data, the HMRC default value for that precursor can be used instead.

## What Senseible does here

Senseible reads billet, ingot and ammonia purchase invoices with their dates and suppliers, so each lot can be matched to a production year. 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.

- [Which year's figure the importer uses](https://senseible.earth/answers/uk-cbam-which-year-emissions-figure)
- [Billets from several mills](https://senseible.earth/answers/uk-cbam-billets-from-several-mills)
- [CBAM Suite](https://senseible.earth/cbam-suite)

Sources: [HMRC, Carbon Border Adjustment Mechanism (CBAM): Policy summary (updated 2 November 2026)](https://www.gov.uk/government/publications/carbon-border-adjustment-mechanism-cbam-policy-summary/carbon-border-adjustment-mechanism-cbam-policy-summary), [HMRC, UK CBAM monitoring, reporting and verification technical guidance (October 2026)](https://assets.publishing.service.gov.uk/media/6ad219fe0f7b53973e02680f/CBAM_technical_guidance.pdf)

Last reviewed 2026-11-03.