We make billets and bars on one site. How does the UK CBAM treat that?

If every billet you make is rolled on site, never sold or used in another process, HMRC lets you define one joint production process. You then monitor emissions and calculate one emissions intensity across melting and rolling together. Sell even part of your billets and the joint approach is not allowed.

The two conditions

1. One installation makes both the precursor (billet) and the complex good (bar).
2. The precursor is not transferred for sale or used in other production processes.

What changes when you qualify

Instead of a separate billet figure that is then added to the rolling mill's figure, you monitor the whole chain as one process. HMRC's step 5, adding precursor emissions, can be skipped because they are already inside the joint total.

When it does not fit

HMRC's own example is an electric arc furnace plant whose crude steel is both rolled on site and sold: because some is sold, the joint approach is not allowed and melting and forming stay as separate processes. If you sell billets in some months, you have to keep them separate for the whole year.

Melt shop plus rolling mill

• Melt shop, including bought-in sponge iron as a precursor: 3,000 tCO2e. Reheating and rolling: 900 tCO2e. Bars produced: 10,000 t.
• All billets rolled on site, so one joint process.
• Emissions intensity: (3,000 + 900) / 10,000 = 0.39000 tCO2e per tonne of bar.
• If 1,000 t of billet had been sold, you would need a billet figure and a bar figure, each from its own process.

Example direct emissions only; UK CBAM does not count electricity.

What Senseible does here

Senseible reads billet sale invoices separately from bar dispatches, so you can show whether any billet left the site. 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.

• Many sizes, one process
• Emissions intensity steps
• CBAM Suite

Sources: HMRC, Carbon Border Adjustment Mechanism (CBAM): Policy summary (updated 2 November 2026), HMRC, UK CBAM monitoring, reporting and verification technical guidance (October 2026)

Last reviewed 2026-11-03.