Default emissions values vs actual verified data: which should you use?
You can calculate your embodied emissions with a government default value or with your supplier's actual, independently verified data, and the choice usually decides how much you pay. Because a mark-up is applied to default values so they are not cheaper than verified data, actual data typically produces a lower charge whenever your overseas producer is cleaner than the default. The catch is lead time: you need the supplier data before the accounting period runs.
The two routes
For each CBAM good you import, your embodied-emissions figure can come from one of two sources:
- The default value. Government publishes one default embodied-emissions value per good, in advance. It is the simple route: no supplier engagement, no verification. You take the published number and apply it.
- Actual verified data. You use the specific, independently verified emissions of the goods you actually imported, obtained from your supplier or producer. It takes work to gather and verify, but it reflects reality rather than a conservative benchmark.
Why the default is the expensive default
The important design feature is that a mark-up is applied to default values, deliberately, so that a default is not cheaper than verified data. The policy reason is to stop importers hiding behind a generous benchmark and to reward those who evidence genuinely lower emissions. The practical consequence for you is that the default is set to be a costly option: if your producer is cleaner than the benchmark, and many modern producers are, the default overstates your emissions and so overstates your charge. Actual verified data is how you claim the lower, true figure.
The size of the mark-up is reported to differ by sector, smaller for fertiliser and larger for other sectors, and to increase over time, but the exact percentages are not yet confirmed in the final legislation. We do not publish specific mark-up percentages until they are verified against the enacted rules; for now the safe statement is simply that an uplift applies and it favours collecting actual data.
Actual data is a lead-time problem, not a paperwork problem. You cannot retrofit verified emissions onto goods you imported months ago without the underlying production data. The businesses that pay less on CBAM are the ones that started asking suppliers for the right figures before the first accounting period opened on 1 January 2027.
When the default might still be right
The default is not always the wrong choice. It can make sense where your import volumes are small enough that the charge is immaterial, where your supplier genuinely cannot provide verified data, or where the cost and effort of verification outweigh the saving. For a low-volume importer near the threshold, the default may be a reasonable, low-effort route. The point is to make the choice deliberately, with a rough sense of the saving, rather than defaulting to the default because it is easier.
What "verified" means in practice
Actual data has to be independently verified to count, not just supplied by the producer on a spreadsheet. That means production route, verified emissions per tonne, and the verification body all matter. The supplier data checklist sets out exactly what to ask for so the data you collect is the data HMRC will accept.
The numbers are still landing
As at 12 July 2026 the per-good default emissions values have not been published, and the mark-up percentages are not confirmed. So any cost estimate that uses a default is working from a placeholder until HMRC publishes the official value. That is why our estimator labels its emissions factor as a placeholder and re-runs the moment the real figures land. The lesson from other decaying tax figures is that the number matters, so we would rather show a labelled placeholder than a confident guess.
Frequently asked questions
Can I choose between default and actual data?
Yes. You may use either actual, independently verified emissions data for the specific goods, or a published default emissions value for the good.
Why does actual data usually cost less?
A mark-up is applied to defaults so they are not cheaper than verified data. Where your producer is cleaner than the default, actual verified data gives a lower embodied-emissions figure and a lower charge.
Are the default values published yet?
Not as at 12 July 2026. One default per good will be published in advance; until then any estimate using a default is working from a placeholder.
Sources
- GOV.UK, Introduction of the Carbon Border Adjustment Mechanism, on the choice between actual verified data and a default value. gov.uk
- GOV.UK, CBAM Policy Summary, on one default per good published in advance and a mark-up applied to defaults. gov.uk
Content current as of 12 July 2026. The default values and mark-up percentages are pending confirmation in the final legislation; we do not publish specific percentages until verified. Re-check the primary source before relying on any figure.
Work out whether actual data is worth it for you
The report shows an estimated cost using a labelled placeholder default and points you to the supplier data that usually lowers it.
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