UK CBAM guidance
UK CBAM default emissions values
Default values are the fallback where verified actual emissions data is unavailable. HMRC says it will publish one default emissions value per CBAM good before CBAM starts.
Last updated: 13 August 2026
When must you use a default?
HMRC’s records guidance says a default emissions value must be used when actual emissions data is not available, or when you do not have evidence that the actual data is verified. This makes the default route an important part of practical CBAM readiness.
What is known now
| Point | Current position |
|---|---|
| Availability | Government default values are to be published ahead of the 1 January 2027 start date. |
| Number of values | HMRC policy says there will be one default emissions value per CBAM good from 2027. |
| Actual vs default | Actual data is possible only with appropriate verification evidence. |
| Precursor goods | Policy allows defaults for precursors even when actual data is used for the final good; the reverse is not permitted. |
How to prepare before the values arrive
- Build the commodity-code and net-weight dataset first.
- Mark supplier emissions data as verified, pending, unavailable or not applicable.
- Model defaults as an unknown input—not a made-up rate—until HMRC publishes them.
- Keep actual-data requests moving so you can choose the supported route later.
A practical caution
Do not copy EU CBAM values or supplier sustainability figures into a UK CBAM calculation and assume they will be accepted. UK CBAM uses its own rules, values and evidence requirements. Follow the current HMRC notice when it is published.
For planning: you can estimate which imports are likely to be exposed before default values are released. Do not present an estimated charge as an HMRC-calculated liability.