# Can a mass-balance low-carbon steel certificate lower our CBAM figure?

Canonical: https://senseible.earth/answers/cbam-mass-balance-green-steel-not-accepted

No. The EU's CBAM Q&A 4.13 says the mass balance chain of custody model cannot be used as proof of traceability in CBAM. A certificate that allocates low-carbon steel on paper does not lower the figure. Embedded emissions are reported per CN code, as a weighted average where batches mix.

## What the Q&A says

The question was asked about fertiliser batches blended in one tank. The answer covers CBAM as a whole: mixed batches of one CN code are reported as a weighted average of the functional unit, and mass balance cannot prove traceability.

## What your precursor figure is

The supplier installation's verified embedded emissions for the CN code you bought, averaged over everything it made under that code in the period. The low-carbon share allocated to your invoice does not change it.

## What does lower it

- Buying from an installation whose verified figure for the code is lower.
- Physical changes at your supplier, more scrap or cleaner reduction, that lower the average for every tonne.
- Better yield at your own plant, so you use less steel per tonne of product.

## Where the certificate may still help

A buyer programme or product footprint standard may accept mass balance claims under its own rules. Check that programme. Keep the claim out of the CBAM file.

## Example: 1,000 t of coil sold as low-carbon

- Supplier makes 100,000 t under one CN code at 2.2 t CO2e per tonne
- It sells 20,000 t as 0.5 t CO2e per tonne by mass balance
- Your 1,000 t in the CBAM figure: 1,000 x 2.2 = 2,200 t CO2e, not 1,000 x 0.5 = 500 t

Example figures.

## What Senseible does here

Senseible's CBAM Suite carries each bought precursor at its supplier's verified figure or the EU default value, never at a mass balance claim. We build it from your records, check every figure in-house, and an accredited verifier we partner with signs it off. Have your own verifier? Send it to them.

- [Build your CBAM figure](https://senseible.earth/cbam-suite)
- [Mass balance or segregation](https://senseible.earth/answers/chain-of-custody-mass-balance-vs-segregation)
- [Precursor from two suppliers](https://senseible.earth/answers/cbam-precursor-from-two-suppliers-weighted-average)

Sources: [European Commission, CBAM Questions and Answers (15 October 2026), question 4.7, 4.8 and 4.13](https://taxation-customs.ec.europa.eu/document/download/013fa763-5dce-4726-a204-69fec04d5ce2_en?filename=CBAM_Questions%20and%20Answers.pdf)

Last reviewed 2026-11-01.