UK CBAM Default Values 2027: How the Treasury Sets Them and What They Cost

UK CBAM default values apply from January 1, 2027 to every import reported without verified actual emissions data, and as of October 12, 2026 not one of those values has been published. HM Treasury sets them by notice under paragraph 11(1) of Schedule 17 to the Finance Act 2026. The wider mechanism is explained in the UK CBAM guide.

The default route covers 5 sectors: aluminium, cement, fertilisers, hydrogen, and iron and steel. It concerns importers at or above the £50,000 threshold for UK CBAM registration, because CBAM is not charged on an importer that is neither registrable nor registered (section 147(1)(a)). The statute lets the Treasury set a default at a level that gives no advantage over measuring, so a default is not designed to be the cheap option.

What Are UK CBAM Default Values?

A UK CBAM default value is the amount of carbon dioxide equivalent that HM Treasury specifies for one tonne of a CBAM good, used to calculate the emissions embodied in an import when no verified actual figure is reported.

The definition sits in regulation 2 of the Emissions and Verification Regulations 2026 (SI 2026/995), made on September 8, 2026 and in force from January 1, 2027. Regulation 4 gives the calculation in one line: "the emissions are the weight of the good multiplied by the default value."

A default value is not the UK CBAM rate. The default value is an emissions quantity, in tonnes of CO2 equivalent per tonne of good. The rate is a price, in pounds per tonne of CO2 equivalent, set per sector and per quarter. A search for a "UK CBAM default rate" mixes the two: the bill needs both figures, and the Treasury publishes them separately.

UK default values are also not the EU's CBAM default values, which the European Commission sets for its certificate-based mechanism. A figure from one regime has no standing in the other. UK law says "embodied" emissions where EU law says "embedded"; the idea is the same.

When UK CBAM Default Values Apply

Two circumstances leave a default value as the only figure a liable person can report: actual emissions data is not available, or the data available does not qualify as verified emissions data.

HMRC's guidance on keeping records for CBAM, published July 16, 2026, names both: a default emissions value must be used if "actual emissions data is not available to you" or "you do not have evidence the emissions data you are reporting has been verified".

The statute frames the default as an option: the Treasury "may by notice set default values that may be used" (paragraph 11(1)), and the actual-emissions method in regulation 5 applies only where "no default value is being used".

Where Supplier Data Is Unavailable

The first circumstance is the plain one: no installation-level figure reaches the importer, as can happen when goods are bought through traders. HMRC's Policy Summary, updated September 9, 2026, says default values mean "the liable person can meet CBAM obligations when actual emissions data is unavailable."

The return then carries the weight of the good and "the level of the default value", an item that regulation 17 of SI 2026/995 adds to the return. No verification report has to be kept for these goods (regulation 16(2)).

Where Supplier Data Fails the Evidence Standard

The second circumstance costs more, because the importer believed it had data. A supplier figure counts only as "verified emissions data" under regulation 10, which means passing the 5 tests listed below.

• Monitoring period: a calendar year. For goods imported before January 1, 2028, the most recent verified year out of the year of import and the year before, or the year of production (regulation 9).
• Methodology: the monitoring requirements HMRC sets by notice under regulation 11.
• Verifier: independent of the importer, the installation and its operator, and accredited for that type of CBAM good (regulation 12(1)).
• Accreditation body: a full member of the Global Accreditation Cooperation Incorporated (regulation 15(1)).
• Opinion: a verification opinion statement that the data are sufficiently accurate (regulation 10(c)), with materiality set at 5% of emissions intensity in the Policy Summary.

A supplier spreadsheet, a self-declared product carbon footprint, or a report from a verifier accredited for a different sector fails these tests. HMRC's draft Emissions and Verification force of law notice adds an installation-level rule: where no appropriate monitoring method exists for a data set, or using one would incur unreasonable costs or be technically infeasible, the published default values "must be used". That notice is a draft with no force of law before January 1, 2027.

The timing trap sits in Schedule 17, paragraph 8(2): "No amendment may be made to replace information on the emissions embodied in CBAM goods determined using default values set under paragraph 11 with such information determined in accordance with regulations under paragraph 10."

On that wording the bar attaches to a return already made: once an accounting period is filed on default values, verified data that arrives later cannot be amended into it. It covers amendments only, so verified data can still go into a later return, or into the first return itself, which covers 2027 and is due by May 31, 2028 (SI 2026/830).

How UK CBAM Default Values Are Set: HM Treasury, Not HMRC

HM Treasury sets UK CBAM default values by published notice. HMRC does not set them, and neither the values nor the method behind them had been published as of October 12, 2026.

The power is paragraph 11(1) of Schedule 17 to the Finance Act 2026. HMRC collects the return and sets the monitoring and verification rules by its own notices. Law and published policy already fix 4 points about the coming notice, listed below.

• Granularity: "From 1 January 2027, there will be one default emissions value set per CBAM good" (Policy Summary), covering CBAM goods and precursor goods (regulation 2).
• Scope: direct emissions only, within the System Boundaries Document, version 1.00 dated July 10, 2026, which applies to actual data and default values alike.
• Revision: a notice "may be amended or withdrawn by a further notice" (section 157(16)).
• Wider powers: values may vary by where emissions were emitted and may cover a portion of a good's emissions (paragraph 11(2)). No notice has used either power.

The instruments behind these points are listed in the UK CBAM legislation guide.

The Published Default Values by Sector

No sector has a published UK default value. The table below records each of the 5 sectors as checked on October 12, 2026, and it will be filled in from the Treasury notice when that notice appears.

Last checked: October 12, 2026. The Policy Summary says default values "will be published in a notice on GOV.UK in advance of CBAM coming into force", and HMRC's CBAM collection on gov.uk says: "HMRC will publish guidance soon on rates and default emissions values for aluminium, cement, fertilisers, hydrogen and iron and steel." Neither gives a date; the July 2026 record-keeping guidance says only "later this year".

EU figures are deliberately absent from this table. CBAM Brief, the site's email service at EUR 199 a month, sends an alert the day a CBAM certificate price, default value, CN code or deadline changes.

How the Default Differs From the Sector Average

The gap between a UK default and the sector average is unknown, because the method has not been published. The UK statute contains no fixed percentage mark-up of the kind the EU uses. It contains a power instead.

Paragraph 11(3) says a default "may be set at a level that ensures that there would not be an advantage to any person liable to CBAM in using the value instead of determining the emissions" under the regulations. Paragraph 11(4) counts two things as an advantage: embodied emissions "being lower if determined using default values", and "not bearing the cost of determining or verifying emissions".

So a default can lawfully sit above typical emissions by enough to cancel the saved verification cost. Whether the Treasury does that, and by how much, depends on the notice. The government's CBAM factsheet of November 28, 2025 promised to "confirm the methodology to be used for their calculation".

What UK CBAM Default Values Cost

The cost of a default value is the weight of the import multiplied by the default value, multiplied by the sector's quarterly CBAM rate, less any carbon price relief. With neither default values nor rates published, that cost cannot be stated in pounds as of October 12, 2026.

The 4 steps of the calculation, each with its legal source, are set out below.

1. Embodied emissions (tCO2e) = weight in tonnes x default value (regulation 4, SI 2026/995).
2. CBAM charge (GBP) = embodied emissions x the sector rate for the quarter in which liability is incurred (section 149(1) and (2), Finance Act 2026).
3. Carbon price relief (GBP) = effective carbon price x emissions subject to a qualifying carbon pricing scheme, capped at the liability (regulation 13, SI 2026/809).
4. CBAM liability (GBP) = charge minus relief (Policy Summary, Figure 1).

The price in step 2 is the statute's "sectoral domestic price", which the Treasury calculates and publishes for each sector and quarter; the UK CBAM rate guide explains its two-step formula. The Policy Summary says rates will be published at the beginning of each quarter from January 1, 2027, with an illustrative example rate in autumn 2026. Neither a rate nor an illustrative rate figure had appeared in HMRC's CBAM collection by October 12, 2026.

Worked Example: Steel at the Default Value

This example is illustrative. The tonnage, the quarter and the absence of relief are assumptions; the two regulatory inputs are unpublished, so they stay as named placeholders.

As arithmetic on the assumed 1,000 tonnes, every 0.1 tCO2e per tonne by which the default exceeds the installation's verified intensity adds 100 tCO2e to the emissions charged, which costs 100 x R pounds.

Worked Example: Aluminium at the Default Value

This example is also illustrative, with the same assumptions and placeholders.

The table shows the full default route. A mixed route also exists, where the producer has verified data for its own process but none for the unwrought aluminium it bought: regulation 7(b) counts that precursor at its default value multiplied by the weight used, inside the regulation 5 calculation. The Policy Summary confirms the mix runs one way only: actual precursor data cannot be used where the final good is on a default value.

UK CBAM Default Values Compared With EU CBAM Default Values

UK and EU default values answer the same question with different machinery: the UK applies a Treasury figure inside a tax return, and the EU applies a Commission figure with a fixed mark-up inside a certificate-based declaration.

The table below compares the two constructions on 9 attributes.

Differences beyond default values are set out in the UK CBAM vs EU CBAM comparison.

Why the Two Regimes Produce Different Numbers

Three design choices separate the two figures for the same tonne of product. Scope comes first: the EU counts indirect emissions for cement and fertilisers, as the embedded emissions guide explains, and the UK charge is based on direct emissions only. Construction comes second: the EU starts from country values and adds a published percentage, while the UK plans one value per good at an undisclosed level.

Pricing comes third. The EU applies its official quarterly certificate price (EUR 82.32 per tCO2e for Q3 2026, published October 5, 2026) to a share of emissions that grows as free allocation is phased out; the UK builds the free-allocation adjustment into the rate itself.

Can One Set of Supplier Data Serve Both Regimes?

Partly: one monitoring exercise at the installation can feed both regimes, but each regime needs its own verified output. The Policy Summary says the UK monitoring and verification methodologies are "broadly designed to support interoperability with the EU CBAM".

Three caveats apply. The UK figure excludes indirect emissions. The functional unit is close to the EU rule but not identical: the System Boundaries Document measures all fertilisers by nitrogen content, while the EU rule (Article 4 of IR (EU) 2025/2547) does so only for some fertiliser codes. And no HMRC document read for this page says an EU verification report is accepted as it stands. The EU supplier data points are listed in the CBAM data requirements guide.

How to Replace a Default Value With Verified Data

Replacing a default value takes 7 steps, and the order matters because of the amendment bar.

1. Identify the installation that produced each good, and the installations behind any precursor goods.
2. Send the operator the System Boundaries Document and the draft Emissions and Verification notice from HMRC's force of law notices page.
3. Fix the monitoring period, a calendar year chosen under regulation 9.
4. Appoint a verifier accredited for that type of good by a qualifying accreditation body.
5. Obtain the verification report, or a good-specific verification summary, for the emissions intensity.
6. Report the verified intensity in the return for the accounting period of import, since a return filed on a default value cannot be amended to actual data.
7. Keep the report or summary for 6 years, beginning with the day after the accounting period (regulation 16(3)).

Who Verifies Emissions Data for UK CBAM?

An independent verifier, accredited by a full member body of the Global Accreditation Cooperation Incorporated, verifies emissions data for UK CBAM. The Policy Summary names the standards: ISO/IEC 17029:2019 and ISO 14065:2020. HMRC's gov.uk collection held no register of UK CBAM verifiers on October 12, 2026; the UK CBAM verifiers page tracks the accreditation route.

Frequently Asked Questions About UK CBAM Default Values

Has HMRC published UK CBAM default values yet?

No. As of October 12, 2026 no UK CBAM default value has been published. HM Treasury, not HMRC, sets them by notice under paragraph 11(1) of Schedule 17 to the Finance Act 2026, and HMRC's Policy Summary says the notice will appear on gov.uk before CBAM comes into force.

Do UK CBAM default values carry a mark-up like EU defaults?

Not a fixed one. The EU adds 10% in 2026, 20% in 2027 and 30% from 2028 (1% for fertilisers). Paragraph 11(3) of Schedule 17 to the Finance Act 2026 sets no percentage: it lets the Treasury set a default at a level that gives no advantage over determining actual emissions.

Does the UK CBAM default value change each year?

No annual schedule exists in law. A Treasury notice can be amended or withdrawn by a further notice under section 157(16) of the Finance Act 2026, and the government's November 28, 2025 factsheet says it is considering an alternative approach to default values after 2027.

Can I use EU default values for a UK CBAM return?

No. Regulation 2 of SI 2026/995 defines a default value as the amount specified in a Treasury notice. Values from Implementing Regulation (EU) 2025/2621 belong to the EU mechanism and have no status in a return to HMRC.

What evidence replaces a UK CBAM default value?

A verified emissions intensity for the good, supported by a verification report or a good-specific verification summary from an accredited, independent verifier. The liable person keeps that document for 6 years under regulation 16 of SI 2026/995.

Does the UK CBAM default value differ by country of origin?

Not in 2027, on the published policy: HMRC's Policy Summary describes one default emissions value per CBAM good. Paragraph 11(2)(a) of Schedule 17 to the Finance Act 2026 allows values that vary by where emissions were emitted, so country-specific values remain legally possible later.

Can a UK CBAM return be amended from a default value to actual data?

No. Schedule 17, paragraph 8(2) of the Finance Act 2026 bars any amendment that replaces default-based emissions with emissions determined from actual data. The choice has to be made when the return is first filed, as the UK CBAM reporting guide explains.