For the start in 2027, the UK is now translating its CBAM framework into detailed secondary legislation. HMRC has issued the first set of statutory instruments and legally binding notices, defining the administrative requirements and technical rules. These new measures establish the practical foundations for CBAM implementation. 

 (Last update on 11/02/2026)

Secondary legislation is setting the rules

The UK Carbon Border Adjustment Mechanism (CBAM) has progressed from principles to detailed rule‑drafting. CBAM itself enters into force on 1 January 2027 – one year later than the EU CBAM.

Primary legislation was introduced in the Finance Bill 2025–26. These core rules will be operationalized through secondary regulations and notices.

On 10 February 2026, HM Revenue & Customs (HMRC), the UK’s tax authority,  opened a technical consultation on the first tranche of draft secondary legislation, with feedback due by 24 March 2026. A second tranche will follow in Spring 2026. Final regulations are expected to be laid later this year.

Together these regulations set a carbon price for imports of specified, carbon‑intensive goods – comparable to that borne by UK producers. The objective is to reduce carbon leakage while supporting the UK’s decarbonisation pathway.

Detailed rules for implementation

A package of secondary legislation is setting a statutory instruments (SI). They form the detailed rules for implementation from 2027 onwards.  HMRC’s Policy Summary offers a living overview.

Administrative provisions

This SI defines the administrative requirements for CBAM:

1. process to register, and the content and timing of CBAM returns;
2. rules on reimbursement;
3. the treatment of weight;
4. and record‑keeping obligations.

It explains the information HMRC expects from importers, the accounting periods (quarterly), and the evidential standards businesses must meet to support their filings.

For importers of CBAM goods, this is the regulation that translates policy into compliance steps: from triggering registration to what your CBAM return must include and how long you must keep your records.

Calculation of CBAM rate and determination of carbon price relief

This SI sets out the technical rules for:

1. calculation of the CBAM rate for each sector;
2. rules for claiming Carbon Price Relief (CPR) where overseas carbon prices (e.g., an ETS price or a carbon tax) have already been paid;
3. currency conversion for CPR;
4. and record‑keeping tied to CPR claims.

This is the technical underpinning for the CBAM charges to be paid. This SI explains the inputs HMRC uses to set sectoral CBAM rates and the evidence to be provided to reduce liability where a qualifying carbon price applied before import. This SI defines the rate‑setting approach and the principles underpinning CPRs.

Transitory provision

For a phasing in of CBAM in the first year, this SI defines the diverging dates and timing related to:

1. registration;
2. payment;
3. accounting periods;
4. and penalties.

These provisions define the internal timetables, cash flow and governance during the inaugural year for importers of CBAM goods before the regular quarterly rhythm resumes. These transitional adjustments are supposed to make CBAM workable from day one.

Notices with force of law

Alongside the SIs, HMRC has published draft notices with force of law. These will sit next to the regulations and provide granular instructions; for example, technical definitions, data fields, formats and evidential requirements that importers must follow when registering, filing a return, or claiming Carbon Price Relief.

In practice, these notices will describe what importing companies need to submit and how, and what will constitute acceptable evidence. They are essential reading for building the internal processes and data flows for 2027.

How to get prepared for 2027

These secondary legislations set the practical CBAM foundation: who registers, what returns must contain, how CBAM rates and CPR are determined, and how the first‑year timetable will work.  

To get ready for 2027, UK companies should take key steps:

• Map scope & triggers: Match your imports to the specified CBAM goods and assess when the £50,000 rolling threshold will trigger registration.
• Design quarterly compliance: Set up processes and schedules for quarterly returns and align cut‑offs with the transitional timing.
• Build data & controls: Configure systems to capture return content, weight, and required records.

HMRC will publish the second tranche of secondary legislation in Spring 2026 and aims to lay final regulations later in 2026. With this, further clarifications on the rules and their practical implementation is expected before the CBAM start. Companies need to keep their implementation plans “living” and anchored in any updates.

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Sources and further information:

• HM Revenue & Customs: CBAM Draft Legislation
• HM Revenue & Customs: CBAM Policy Summary

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