UK CBAM Registration and Liability Thresholds: A Compliance Manager's Guide to HMRC Registration, Threshold Monitoring and 2027 Readiness
- Ahtesham Shaikh
- Jun 9
- 28 min read
CBAM Journal | Sekason Research Limited, London Published June 2026 | Compliance Intelligence Report
This report is provided for informational purposes only. It does not constitute legal, financial, or regulatory advice. Readers should obtain independent professional advice before making compliance decisions.
Executive Summary
From 1 January 2027, any business importing steel, aluminium, cement, fertilisers, or hydrogen into the UK must register with HMRC as a UK CBAM liable person once its import values cross £50,000 — and the registration obligation can be triggered at any point in the year through either a rolling 12-month historical test or a 30-day forward-looking assessment of expected imports.
The operational challenge is not understanding the threshold but operationalising the two tests: most businesses do not currently hold their import data in a consolidated, commodity-code-level format suitable for either calculation. HMRC has not yet published final penalty figures for registration failures, but a business that has made no attempt to assess its position before 1 January 2027 carries material regulatory, financial, and governance exposure.
The registration window is expected to open in late 2026. Businesses that will clearly exceed £50,000 in covered imports should not wait for a formal threshold-crossing event — they should register as soon as the HMRC portal opens. The first CBAM return and payment deadline is 31 May 2028, covering the full 2027 accounting period, and the data collection infrastructure required for that return must be operational from day one of the regime.
Key Findings
The £50,000 threshold operates through two simultaneous tests — one backward-looking (rolling 12 months) and one forward-looking (next 30 days). Both must be monitored continuously.
Electricity is excluded from UK CBAM scope. Five sectors are covered: steel, aluminium, cement, fertilisers, and hydrogen.
As of June 2026, final penalty regulations for registration failures have not been published. The legislative framework is the Finance Act 2026, with secondary legislation on emissions, verification, and administration still in consultation.
The registration window is expected in late 2026. Businesses have 30 days from becoming liable to register.
The first CBAM return and payment deadline is 31 May 2028, covering the full 2027 accounting period. Data collection infrastructure must be operational from 1 January 2027.
Executive Action Checklist
Determine by September 2026 whether your business imports goods in any of the five covered sectors above the £50,000 threshold using both the backward-looking and forward-looking tests.
Assign internal ownership of the threshold monitoring process to a named function — this decision should not default to customs alone.
Establish a monthly import value aggregation process drawing on customs declarations and commodity code data before the registration window opens.
Document your registration determination — whether you register or conclude that you do not meet the threshold — with supporting evidence that could withstand HMRC scrutiny.
Begin supplier engagement on embedded emissions data now; this data is required for the first CBAM return, not the registration itself, but the lead time for obtaining it from overseas suppliers is substantial.
Regulatory Context: Understanding UK CBAM Registration
Why the UK Introduced CBAM
The UK Carbon Border Adjustment Mechanism addresses a specific structural risk in carbon pricing policy: carbon leakage. When domestic producers face carbon costs under the UK Emissions Trading Scheme (UK ETS) that overseas competitors do not, UK importers gain a cost advantage by sourcing from jurisdictions with weaker or absent carbon pricing.
Left unaddressed, this dynamic undermines both the environmental integrity of the UK ETS and the competitive position of UK manufacturers in carbon-intensive sectors. The UK CBAM counters this by applying a carbon cost adjustment to imported goods equivalent to what a UK producer would have paid under the UK ETS on the embedded emissions of those goods.
The mechanism was confirmed by the UK Government on 30 October 2024 following a policy design consultation, and enacted through the Finance Act 2026. The policy objective is to create a level playing field between UK domestic producers — who pay for their emissions under the UK ETS — and overseas producers who do not face equivalent carbon pricing. Qualifying foreign carbon prices already paid in the country of origin attract relief against the UK CBAM charge, preventing double-counting.
UK CBAM Scope and Covered Goods
Five sectors fall within UK CBAM scope from 1 January 2027: iron and steel, aluminium, cement, fertilisers, and hydrogen. Electricity — which is covered under the EU CBAM — is expressly excluded from the UK's initial scope, a deliberate policy decision confirmed in the Government's October 2024 consultation response. Businesses importing goods in any of these five sectors must assess whether their import volumes bring them within the registration threshold.
The table below sets out the initial scope position for UK and EU CBAM.
Table 1: UK CBAM Scope — Covered and Excluded Sectors
Sector | UK CBAM Scope (from 1 Jan 2027) | EU CBAM Scope (from 1 Jan 2026) |
Iron & Steel | Covered | Covered |
Aluminium | Covered | Covered |
Cement | Covered | Covered |
Fertilisers | Covered | Covered |
Hydrogen | Covered | Covered |
Electricity | Excluded | Covered |
The boundary between in-scope and out-of-scope goods at the product classification level is governed by commodity codes specified in the Finance Act 2026 and associated secondary legislation. Businesses importing processed or downstream products derived from covered materials —
for example, fabricated steel components — should verify whether those products fall within the commodity code scope. Published guidance as of June 2026 does not fully resolve all product classification edge cases, and businesses with borderline classifications should seek confirmation from HMRC or qualified customs advisers before concluding that they are outside scope.
Evolution of UK CBAM Policy
The UK CBAM legislative framework has developed through several distinct stages, each of which affects what is currently certain and what remains subject to further regulatory development. A policy design consultation was conducted prior to October 2024, responses were analysed, and the Government published its response on 30 October 2024, confirming the decision to proceed. The Finance Act 2026 enacted the primary legislative framework for UK CBAM, establishing the core liability structure, the registration threshold, and the basic mechanics of the charge.
Secondary legislation covering the operational detail — including emissions calculation methodologies, verification requirements, and administrative procedures — has been subject to separate consultation. The Government launched a consultation on draft secondary legislation on 9 April 2026, covering emissions and verification regulations.
A further consultation on administrative regulations, including carbon price relief calculations, ran during February and March 2026. As of June 2026, those secondary regulations have not been finalised. This gap is material: until the emissions and verification regulations are confirmed, businesses cannot finalise their embedded carbon calculation methodology, and the full detail of the HMRC registration process has not been formally published.
Table 2: UK CBAM Regulatory Development Timeline
Date | Event |
Pre-October 2024 | Policy design consultation conducted |
30 October 2024 | Government consultation response published; UK CBAM confirmed |
2026 | Finance Act 2026 enacted — primary CBAM legislative framework |
February–March 2026 | HMRC consultation on draft administrative regulations |
9 April 2026 | Consultation launched on draft emissions and verification regulations; Policy Summary published |
Late 2026 | Expected HMRC registration window opens |
1 January 2027 | UK CBAM enters into force |
31 December 2027 | End of first accounting period |
31 May 2028 | First return and payment deadline |
The practical implication of the secondary legislation gap is that compliance managers must build their internal frameworks on the primary legislation and policy summary guidance that is available, whilst remaining alert to finalised secondary legislation that may require adjustments to their methodologies before 1 January 2027.
Compliance Obligations: Who Must Register and Why
Definition of a UK CBAM Liable Person
A business becomes a UK CBAM liable person when it imports CBAM goods into the UK and its import values meet or exceed the registration threshold. The liable person is the importer of record — the entity responsible for the customs declaration at the point of entry into the UK. This matters for businesses that use customs brokers, freight forwarders, or agents to handle their import declarations: the obligation attaches to the importer of record, not to the agent acting on their behalf. Routing imports through an intermediary that handles the customs paperwork does not transfer the UK CBAM liability — the underlying importing entity carries it.
The liability framework applies to businesses of all sizes meeting the threshold conditions, with one relevant carve-out: the £50,000 threshold is specifically designed to exclude very small importers from the compliance burden. However, the threshold operates at the level of the individual legal entity importing CBAM goods, and published guidance as of June 2026 does not confirm how the threshold applies where multiple group companies share a parent but operate separate import accounts. Businesses with corporate structures involving multiple importing entities within a group should not assume that the threshold applies at group level rather than at entity level — this remains a point requiring clarification from HMRC guidance or formal ruling.
Based on available guidance, the threshold applies to the aggregate value of all CBAM goods imported rather than being calculated per sector or per commodity code in isolation. A business importing both steel and aluminium therefore combines those import values when assessing threshold exposure. This interpretation requires confirmation in secondary legislation or HMRC guidance once published — businesses with multi-sector import profiles should seek that confirmation before the registration window opens.
The UK CBAM regime applies to importers of record in the UK. Overseas suppliers carry no direct UK CBAM registration obligation, though their cooperation on embedded emissions data is required for the importing business to complete its CBAM return.
The £50,000 Registration Threshold Explained
£50,000 is the import value at which a business becomes a UK CBAM liable person — but the mechanics of how that threshold is applied contain several points of confusion that published guidance does not fully resolve. The threshold is assessed against the customs value of CBAM goods imported, which is the value declared on the import customs declaration. This is the transaction value of the goods as defined under UK customs valuation rules, and it generally reflects the price paid or payable, adjusted in accordance with those rules. It does not include import duty, VAT, or other charges applied after the goods enter the UK.
Three specific ambiguities in the current guidance warrant direct attention.
First, based on available guidance, the threshold applies to the aggregate value of all CBAM goods — not to each sector or commodity code in isolation. A business importing £30,000 of steel products and £25,000 of aluminium products in a 12-month rolling period has, on the available interpretation, crossed the £50,000 threshold and should register, even though neither individual commodity stream crosses the threshold on its own. Confirmation of this interpretation should be sought once secondary legislation is finalised.
Second, published guidance does not confirm how businesses with multiple legal entities within a corporate group should apply the threshold. Until HMRC publishes clarifying guidance, each importing legal entity should be assessed independently against the threshold.
Third, the customs value used for threshold purposes is the value declared on the customs declaration. Businesses that do not routinely review their customs entries at commodity code level — or who rely on freight forwarders to complete declarations without internal review — may lack the data infrastructure to aggregate CBAM import values reliably. This is an operational gap that must be addressed before the registration window opens.
Table 3: Threshold Calculation Framework
Scenario | Steel Imports (12 months) | Aluminium Imports (12 months) | Total CBAM Value | Threshold Crossed? |
A | £20,000 | £15,000 | £35,000 | No |
B | £30,000 | £25,000 | £55,000 | Yes |
C | £48,000 | £0 | £48,000 | No |
D | £48,000 | £5,000 | £53,000 | Yes |
E | £0 | £52,000 | £52,000 | Yes |
The threshold is live continuously, not assessed at an annual review date. A business that has not previously crossed £50,000 must register as soon as its rolling 12-month total reaches that figure, or as soon as it expects to reach that figure within 30 days.
Backward-Looking Test
The backward-looking test requires a business to calculate the total customs value of CBAM goods imported in the preceding 12 calendar months and compare that figure against the £50,000 threshold. If the rolling total reaches or exceeds £50,000, the business is a liable person and must register with HMRC within 30 days of crossing that threshold. The 12-month window is rolling, not fixed to a calendar year — which means the test must be re-run at regular intervals, not solely at a year-end review.
The data inputs required to run this test reliably are:
Import customs declarations for all entries where CBAM-covered goods were imported
Commodity codes for each entry, to confirm which imports fall within CBAM scope
Declared customs values for each CBAM-covered entry
A consolidated running total aggregating values across all suppliers, commodity codes, and entry points
The operational friction in this process is substantial for most businesses. Customs declarations are typically managed by freight forwarders or customs brokers and are not routinely consolidated by the importing business into a structured data set at commodity code level.
A business importing steel from three different suppliers through two different ports, using two different freight forwarders, will have its CBAM import data distributed across multiple systems and agents. Without a deliberate data aggregation process, that business cannot run a reliable backward-looking test.
Table 4: Monthly Threshold Monitoring Model — Backward-Looking Test
Month | CBAM Imports That Month (£) | Rolling 12-Month Total (£) | Threshold Status |
July 2026 | 3,000 | 24,000 | Below threshold |
August 2026 | 5,500 | 29,500 | Below threshold |
September 2026 | 8,000 | 37,500 | Below threshold |
October 2026 | 7,000 | 44,500 | Below threshold |
November 2026 | 6,500 | 51,000 | Threshold crossed — register within 30 days |
December 2026 | 4,000 | 55,000 | Registered |
Compliance managers should run this calculation monthly as a minimum. In periods of high import activity — for example, ahead of seasonal purchasing cycles or following changes to supplier arrangements — the monitoring frequency should increase. The point of threshold crossing is also the point at which the 30-day registration clock starts.
Forward-Looking Test
The forward-looking test requires a business to assess whether it expects to import £50,000 or more of CBAM goods in the next 30 days. If that expectation is met, the business must register immediately — it cannot wait until the imports actually occur. This test exists to prevent businesses from registering only after they have already become liable, and it introduces a compliance obligation that is prospective rather than historical.
The practical difficulty in this test is significant. An expectation of £50,000 in CBAM imports over 30 days must be based on something — typically purchase orders, confirmed shipment schedules, or supply contracts. But purchase orders are frequently revised, shipment dates move, and import values change between order confirmation and customs declaration. A business that expects £55,000 of steel imports in the next 30 days based on its current purchase order book may find that actual imports come in at £44,000 due to part-shipments or supplier delays.
Published guidance does not specify how frequently the forward-looking assessment must be formally re-run, nor what level of documentation is required to support it. The prudent position is to run the forward-looking test alongside the backward-looking test on a monthly basis, document the assessment at that point in time, and retain the purchase order data that supported the conclusion.
Table 5: Forward-Looking Test Scenarios
Scenario | Confirmed POs (Next 30 Days) | Expected CBAM Value | Test Result | Action Required |
A | 3 confirmed POs for steel | £62,000 | Threshold expected to be crossed | Register immediately |
B | 2 confirmed POs, values uncertain | £35,000–£55,000 | Uncertain — range straddles threshold | Document assessment; take conservative position |
C | No confirmed POs in next 30 days | £0 | Threshold not expected | Document nil assessment |
D | 1 large PO, part-shipment likely | £70,000 PO; £30,000 expected in 30 days | Threshold not crossed in 30-day window | Monitor actual shipment schedule |
In Scenario B — where the range of expected imports straddles the £50,000 threshold — the defensible approach is to treat the forward-looking test as triggered and register. An overly optimistic assessment that falls below £50,000 when the actual outcome crosses it creates penalty exposure. The administrative cost of registering and subsequently deregistering, if that option becomes available under the final regulations, is lower than the risk of operating as an unregistered liable person.
Registration Process With HMRC
The expected UK CBAM registration process requires a business to notify HMRC once the threshold conditions are met and to provide information required to establish its liable person status. Under the published framework, registration must occur within 30 days of the threshold being crossed, whether through the backward-looking or forward-looking test. The Finance Act 2026 and the April 2026 Policy Summary confirm this general structure.
The specific information fields required for HMRC registration have not been confirmed in published guidance as of June 2026. Businesses should monitor the GOV.UK CBAM guidance pages for portal details when the registration window opens in late 2026.
The registration workflow below reflects the confirmed framework and should be treated as provisional in respect of the specific HMRC portal process, which is subject to final secondary legislation.
Registration Workflow — Step-by-Step Process
Run the backward-looking test: aggregate all CBAM imports over the preceding 12 months by customs value.
Run the forward-looking test: assess expected CBAM imports in the next 30 days using confirmed purchase order data.
If either test indicates the £50,000 threshold is met or exceeded, commence registration within 30 days.
Gather required business identification information and CBAM import data.
Access the HMRC CBAM registration portal when it becomes available (expected late 2026).
Submit registration and retain a copy of the submission and confirmation.
Document the evidence base for the registration determination and store it for audit purposes.
The transitional arrangements for the first year of implementation — referenced in the HMRC Factsheet of November 2025 — have not been fully specified in available guidance. Businesses that will clearly be above the threshold from 1 January 2027 should plan to register as soon as the HMRC registration portal opens, rather than waiting until they have formally crossed the threshold under the live regime.
Key Dates and Deadlines
Chronological Compliance Timeline
The table below sets out every material milestone from UK CBAM confirmation through to the first return deadline. Entries in bold represent hard compliance deadlines with direct registration or reporting consequences.
For businesses that will clearly exceed the £50,000 threshold from 1 January 2027 — which includes the majority of mid-to-large steel and aluminium importers — the registration window in late 2026 is the critical action point. Businesses should not treat 1 January 2027 as the point at which registration activity begins; it is the point by which registration should already be complete.
Registration Window and Trigger Events
The registration window is expected to open in late 2026, providing businesses with a preparation period before the regime goes live. The exact opening date of the HMRC registration portal has not been published as of June 2026. Businesses must not rely solely on HMRC notification that the window is open — they should monitor GOV.UK CBAM guidance pages directly for the portal launch announcement.
Table 6: Registration Trigger Events and Required Actions
Trigger Event | Test Type | Required Action | Deadline |
Rolling 12-month CBAM import value reaches £50,000 | Backward-looking | Register with HMRC | Within 30 days of threshold crossing |
Expected CBAM imports in next 30 days reach £50,000 | Forward-looking | Register with HMRC | Immediately upon expectation being formed |
UK CBAM enters into force on 1 January 2027 | N/A | Data collection for first accounting period must begin | 1 January 2027 |
First accounting period ends | N/A | Prepare CBAM return | 31 December 2027 |
First return and payment due | N/A | Submit return and pay CBAM liability | 31 May 2028 |
Before the registration window opens, businesses should have completed the following: confirmed which of their imported goods fall within CBAM scope; run the backward-looking test against their import history to assess current threshold position; established the data sources and internal process for running the forward-looking test monthly; assigned ownership of the registration process to a named individual or function; and documented their current threshold assessment with supporting evidence.
Financial Exposure and Risk
Registration Failure Risk
Failing to register with HMRC once the threshold conditions are met creates direct legal non-compliance from 1 January 2027. A business operating above the £50,000 threshold that has not registered is importing CBAM-covered goods without the required authorisation and accumulating CBAM liability without the mechanism to discharge it.
HMRC has not published final penalty regulations for UK CBAM registration failures as of June 2026. The Finance Act 2026 establishes the primary framework, and penalty provisions are expected to be set out in secondary legislation still under consultation.
The absence of published penalty figures does not reduce the regulatory risk — it increases uncertainty in risk modelling. Compliance managers and CFOs preparing board-level governance submissions should record this uncertainty explicitly rather than treating unconfirmed penalties as immaterial. In comparable UK tax regimes, HMRC applies penalty structures based on the degree of culpability — reasonable care, careless, or deliberate — and the potential lost revenue. A business that has made no attempt to assess its UK CBAM registration position before 1 January 2027 is likely to be assessed as careless or worse in any future enforcement action.
The reputational dimension is a secondary but real risk. UK CBAM compliance will be visible to customers and counterparties in the supply chain, and non-compliance by a UK importer may affect supplier relationships, customer procurement requirements, and insurance arrangements as the regime matures.
Carbon Cost Exposure
Registration with HMRC is not itself a cost event — it creates the administrative framework through which CBAM liability is calculated and paid. The financial exposure arises when a registered business submits its CBAM return and pays the carbon charge calculated on its imported embedded emissions. The charge is linked to the UK carbon price benchmark and provides relief for qualifying carbon prices already paid in the country of origin.
The financial stakes of the registration decision run in both directions. A business that registers when it should not — for example, because it incorrectly calculated that it had crossed the threshold — incurs administrative compliance cost without a corresponding liability. A business that fails to register when it should have done accumulates unquantified liability that will crystallise when HMRC identifies the non-compliance. For mid-sized importers of steel or aluminium with significant embedded carbon profiles, the accumulated charge across a full accounting year could be material.
The first payment deadline is 31 May 2028, covering the full 2027 accounting period. Businesses with treasury or cash flow planning cycles should factor this liability into financial planning from the point of registration — not from the point at which the return is due.
Governance and Audit Risk
A poorly documented registration determination creates governance and audit risk that existing market content rarely addresses. HMRC operates a risk-based compliance approach across all tax regimes, and the introduction of a new regime — particularly one with significant revenue implications — typically results in a period of active compliance activity in the early years of implementation.
A business that cannot produce clear evidence of how it assessed its CBAM registration position — whether that conclusion was "we are liable" or "we are not liable" — is exposed in any HMRC review.
The HMRC Audit Defence Checklist below identifies the minimum documentation standard that a business should maintain.
Table 7: HMRC Audit Defence Checklist
Document | Purpose | Recommended Retention |
Backward-looking test calculation with underlying data | Evidence of threshold assessment | 6 years minimum |
Forward-looking test assessment with supporting PO data | Evidence of prospective threshold monitoring | 6 years minimum |
Commodity code analysis confirming which goods are CBAM-covered | Evidence of scope determination | 6 years minimum |
Written registration determination signed by responsible officer | Internal governance record | 6 years minimum |
HMRC registration confirmation | Proof of registration | Indefinitely |
Monthly threshold monitoring records | Evidence of continuous monitoring | 6 years minimum |
Board or senior management sign-off on CBAM compliance framework | Governance evidence | 6 years minimum |
The internal sign-off trail matters as much as the underlying calculations. A threshold assessment prepared by the customs team but never reviewed by finance or compliance — and never presented to senior management — creates a governance gap. HMRC scrutiny of new regime compliance frequently examines not only whether the right answer was reached but whether the organisation had an appropriate process for reaching it.
Sector-Specific Impact Analysis
The five sectors within UK CBAM scope carry different registration risk profiles based on typical import volumes, product classification complexity, and the operational challenge of obtaining embedded emissions data from overseas suppliers. The sector exposure matrix below provides a comparative overview.
Steel Importers
Steel importers face the highest combined registration and compliance risk of any covered sector. The sector is likely the largest affected by CBAM import volumes among the five covered sectors, and the commodity code range covers a broad spectrum of flat and long products, tubes, pipes, and processed forms. A mid-sized UK steel service centre or manufacturer importing semi-finished or finished steel products will, in most cases, cross the £50,000 threshold well before the end of a rolling 12-month period.
The product classification challenge is real but manageable: the primary difficulty lies in distinguishing CBAM-covered steel products from processed or fabricated downstream products that may fall outside the commodity code scope. Steel importers should audit their full import commodity code list against the Finance Act 2026 scope provisions before the registration window opens.
The embedded carbon data challenge is more significant — steel production routes vary significantly, and this variation has direct implications for embedded carbon intensity that UK CBAM reporting will need to capture. Many overseas steel suppliers will not have pre-existing embedded carbon data in the format required for UK CBAM reporting, and this should be confirmed with key suppliers before 1 January 2027.
Aluminium Importers
Aluminium importers face a similarly high likelihood of crossing the registration threshold, given that primary aluminium products carry significant unit values. The sector-specific classification issue worth monitoring is the distinction between primary aluminium (ingots, billets, wire rod) and downstream aluminium products such as extrusions, rolled sheet, and castings — not all of which may fall within CBAM scope depending on their commodity code.
Businesses importing aluminium in processed or semi-fabricated forms should verify their scope position explicitly before the registration window opens.
Aluminium production is electricity-intensive, and the carbon intensity of electricity used in smelting varies significantly by origin. This variation will be material to CBAM charge calculations, and the embedded carbon data challenge for aluminium importers is therefore not simply a reporting burden but a commercially significant variable that affects the level of CBAM charge liability.
Cement Importers
Cement importers are less likely than steel or aluminium importers to cross the £50,000 threshold in the majority of cases, given that UK cement imports are dominated by a smaller number of specialist importers and major construction materials distributors. Businesses in this category that do import cement at scale will typically cross the threshold readily. The product classification challenge is relatively contained — clinker, cement, and certain lime products are the primary covered goods.
Cement production generates both process emissions and fuel combustion emissions. The calculation methodologies for these dual emission sources are relatively well established in the EU CBAM framework that preceded the UK regime, and businesses with EU CBAM experience — either directly or through their overseas suppliers — may find that embedded carbon data is more accessible for cement than for steel or fertiliser imports.
Fertiliser Importers
Fertiliser importers face registration risk that varies considerably by product type and purchasing pattern. Nitrogenous fertilisers represent the most carbon-intensive product category within the covered goods, and embedded carbon intensity varies significantly depending on feedstock source and production efficiency. Fertiliser importers sourcing from origins where production methods differ materially from Western European standards should anticipate significant embedded carbon variation between supplier origins.
The registration threshold question for fertiliser importers depends heavily on import frequency and contract structure. Bulk purchasers acquiring fertilisers on seasonal contracts may cross the £50,000 threshold within a single large consignment. Businesses that operate on a seasonal purchasing pattern — with significant spring purchases ahead of the growing season — face a forward-looking test risk in early calendar months that demands specific attention to their January and February purchase order positions.
Hydrogen Importers
Hydrogen importers currently represent the lowest registration risk of the five covered sectors, primarily because commercial-scale hydrogen imports into the UK remain limited as of 2026. The hydrogen import market is in its early development, and the import volumes of most UK businesses are likely to fall below the £50,000 threshold in the initial years of CBAM implementation. However, this position is expected to change as the UK hydrogen economy develops over the 2026–2030 period.
The embedded carbon challenge for hydrogen is the most complex of any covered sector. The carbon intensity of hydrogen varies significantly by production method — a distinction that will be central to CBAM charge calculations for hydrogen imports. Businesses beginning to develop hydrogen import strategies should factor CBAM compliance requirements into supplier selection and contracting from the outset, given that production route will directly determine the CBAM charge applicable to each consignment.
Practical Action Framework
UK CBAM Registration Decision Tree
The decision tree below provides a sequential framework for determining whether a business is a UK CBAM liable person. Every branch ends in a defined compliance action or a confirmed non-liability determination.
UK CBAM Registration Decision Tree
Does your business import goods into the UK?
No → UK CBAM does not apply. No action required.
Yes → Proceed to Step 2.
Do any of your imported goods fall within the following sectors: iron and steel, aluminium, cement, fertilisers, hydrogen?
No → UK CBAM does not apply to your imports. Document this determination with your commodity code analysis. Review annually in case of scope expansion.
Yes → Proceed to Step 3.
Run the backward-looking test: what is the total customs value of CBAM goods imported in the preceding 12 months?
£50,000 or more → You are a UK CBAM liable person. Register with HMRC within 30 days. Proceed to the registration process.
Below £50,000 → Proceed to Step 4.
Run the forward-looking test: do you expect to import £50,000 or more of CBAM goods in the next 30 days?
Yes → You are a UK CBAM liable person. Register with HMRC immediately.
No → You do not currently meet the threshold. Document this determination with the date and underlying purchase order data. Repeat this assessment monthly.
After completing Steps 3 and 4, if not currently liable: set up monthly monitoring using the threshold monitoring framework in Section 6.3. The registration obligation arises at the point either test is met — not at a fixed review date.
Threshold Monitoring Framework
Most businesses importing CBAM-covered goods do not currently hold their import data in a format that makes either threshold test straightforward to run. The data is typically distributed across customs brokers' systems, freight forwarder records, internal purchase ledger entries, and HMRC import records — with no consolidated view at commodity code level. Building a monthly monitoring process is therefore an infrastructure task as much as a compliance task.
The Monthly Monitoring Dashboard Template below defines the minimum data inputs required and assigns functional ownership.
Table 8: Monthly Monitoring Dashboard Template
Data Input | Source | Responsible Function | Frequency |
Customs declarations — CBAM commodity codes | Customs broker / HMRC CDS records | Customs/Logistics | Monthly |
Declared customs values per CBAM entry | Customs declarations | Customs/Logistics | Monthly |
Purchase orders for CBAM goods — next 30 days | Procurement system | Procurement | Monthly |
Expected import values — forward-looking estimate | PO values + shipment schedules | Procurement + Finance | Monthly |
Running 12-month CBAM total | Aggregated from customs data | Compliance/Finance | Monthly |
Forward-looking 30-day CBAM total | PO data aggregation | Compliance/Finance | Monthly |
Threshold status assessment | Calculation output | Compliance Lead | Monthly |
Assessment sign-off | Compliance Director / Finance Director | Senior Management | Monthly |
The monitoring cycle should run in the first week of each month, covering the preceding month's actual imports and the next 30 days' expected imports. The output of each cycle — the threshold status assessment and sign-off — should be retained as part of the compliance evidence register. Where the running total is approaching £50,000, the monitoring frequency should increase to fortnightly.
Internal Governance Structure
Registration decisions made in isolation by a single function create accountability and evidence gaps that become problematic under HMRC scrutiny. The threshold monitoring process draws on data held by at least three functions — customs/logistics, procurement, and finance — and the compliance determination requires a level of regulatory understanding that sits with compliance or legal. A governance model that assigns clear ownership across all relevant functions is a prerequisite for producing a defensible compliance record, not an administrative formality.
Table 9: CBAM Registration Governance RACI Matrix
Activity | Compliance/Legal | Tax | Procurement | Customs/Logistics | Finance |
Scope determination (commodity codes) | A | C | I | R | I |
Backward-looking threshold calculation | A | C | I | R | C |
Forward-looking threshold assessment | A | I | R | C | C |
Registration determination and sign-off | R | C | I | C | A |
HMRC registration submission | R | C | I | I | I |
Monthly monitoring process | A | I | R | R | C |
Evidence register maintenance | R | I | I | I | C |
Board/senior management reporting | A | I | I | I | R |
R = Responsible; A = Accountable; C = Consulted; I = Informed
The RACI makes explicit what the default informal approach obscures: the customs function holds the raw data, but the compliance function carries the accountability for the determination. Finance carries accountability for the registration submission decision alongside compliance. Procurement owns the forward-looking data. Without a formal RACI, these overlapping responsibilities default to the loudest voice or the busiest inbox, and the evidence trail fractures.
Registration Readiness Roadmap
The roadmap below runs from July 2026 through May 2028. Every milestone is a specific, completable task with a named responsible function and a defined output. General review activities that cannot be signed off as complete are excluded.
Table 10: UK CBAM Registration Readiness Roadmap — Q3 2026 to Q2 2027
Month | Action | Responsible Function | Output Required |
July 2026 | Identify all imported commodity codes; map against Finance Act 2026 CBAM scope | Customs/Logistics | Confirmed scope inclusion/exclusion list per commodity code |
July 2026 | Appoint named CBAM Compliance Lead | Senior Management | Named individual confirmed in writing |
August 2026 | Extract 12 months of customs declarations for CBAM-covered commodity codes | Customs/Logistics | Consolidated import data file |
August 2026 | Calculate current backward-looking threshold position | Compliance/Finance | Written threshold assessment with supporting data |
August 2026 | Establish procurement data feed: PO values for CBAM-covered goods, next 30 days | Procurement | Live PO report format agreed |
September 2026 | Implement monthly monitoring dashboard; run first cycle | Compliance | First completed dashboard with sign-off |
September 2026 | Establish compliance evidence register; file July and August assessments | Compliance | Evidence register created and populated |
September 2026 | Formalise RACI and brief all relevant functions | Compliance Lead | RACI document signed off by function heads |
October 2026 | Review finalised secondary legislation when published; update methodology if required | Compliance/Tax | Confirmed methodology document |
October 2026 | Monitor HMRC CBAM portal launch announcement on GOV.UK | Compliance | Alert mechanism in place |
November 2026 | Complete HMRC registration (if portal is open and threshold is met or expected) | Compliance | HMRC registration confirmation obtained |
December 2026 | Confirm embedded carbon data collection process with key suppliers | Procurement | Supplier engagement log; data format confirmed |
January 2027 | UK CBAM live — commence systematic import data recording for first accounting period | Customs/Logistics/Compliance | Data collection process operational |
January–December 2027 | Run monthly monitoring; update threshold position; maintain evidence register | Compliance | Monthly dashboard records |
Q1 2028 | Compile data for first CBAM return | Compliance/Finance | Draft return ready for review |
31 May 2028 | Submit first UK CBAM return and payment | Compliance/Finance | Submitted return and payment confirmation |
Evidence and Record-Keeping Framework
The compliance evidence register is the single most important operational output of a UK CBAM registration process. HMRC will not accept a verbal or retrospective account of how a registration determination was made — it will look for a contemporaneous, structured record. The Compliance Evidence Register below specifies the documents required, their purpose in a registration defence, and the minimum recommended retention period.
Table 11: Compliance Evidence Register
Document | Purpose in Registration Defence | Retention Period |
Commodity code scope analysis (dated) | Demonstrates that the business assessed which goods are CBAM-covered before making its registration determination | 6 years from date of determination |
Backward-looking threshold calculation with underlying customs data | Provides the arithmetical basis for the registration decision | 6 years from date of calculation |
Forward-looking threshold assessment with PO data | Documents the prospective assessment and the data used to support it | 6 years from date of assessment |
Monthly monitoring records (running 12-month total and 30-day forward estimate) | Shows continuous monitoring rather than one-off assessment | 6 years from each record date |
Registration determination document (signed by Compliance Lead and Finance Director) | Internal governance record establishing who reached the decision and on what basis | 6 years from date of determination |
HMRC registration confirmation | Proof that registration was completed and accepted | Indefinitely |
Correspondence with HMRC regarding registration queries | Documents any HMRC clarifications sought and received | 6 years from date of correspondence |
Board or senior management briefing note | Demonstrates appropriate governance oversight | 6 years from date of briefing |
Supplier embedded carbon data (for first CBAM return) | Required for return preparation; also evidences due diligence | 6 years from return date |
Every document in this register should be stored in a designated CBAM compliance folder with version control and access restricted to named individuals. The documents should be structured so that, in the event of an HMRC enquiry, the compliance team can produce a complete chronological record from scope determination through to registration submission without relying on institutional memory or informal records.
Strategic Outlook (2026–2027)
Expected Regulatory Developments
Three areas of secondary legislation remain outstanding as of June 2026 and will affect how businesses finalise their UK CBAM compliance methodologies. First, the emissions and verification regulations — subject to the consultation launched on 9 April 2026 — will set the detailed methodology for calculating embedded emissions, the standards for third-party verification, and the default values applicable where supplier-specific data is unavailable.
Until these regulations are finalised, businesses cannot confirm that their emissions calculation approach is compliant. Second, the administrative regulations consulted on during February and March 2026 will govern the HMRC registration process, reporting procedures, and carbon price relief calculations. Third, the HMRC online portal and guidance for the registration process is expected to launch in late 2026 alongside the opening of the registration window.
The Government has not published a confirmed timeline for finalisation of the secondary legislation as of the research date. The April 2026 consultation on emissions and verification regulations is the most urgent gap from a compliance planning perspective — without confirmed calculation methodologies, businesses preparing embedded carbon data collection processes are working to draft parameters. Compliance managers should track the GOV.UK CBAM legislation page and the HMRC CBAM guidance page for updates, and should establish an internal alert process to ensure secondary legislation is reviewed promptly upon publication.
Likely HMRC Enforcement Priorities
HMRC's approach to new regime implementation — based on its behaviour at the introduction of comparable frameworks including the UK ETS and post-Brexit import VAT — follows a predictable pattern. The first one to two years of a new regime typically involve active outreach, compliance support activity, and targeted reviews of larger businesses rather than enforcement actions against smaller importers.
This does not mean that businesses above the £50,000 threshold that have not registered face low risk — HMRC risk models for new regimes typically identify the largest potential liabilities first, and a mid-to-large steel importer that is clearly above threshold and has not registered will be visible.
The registration and documentation failures most likely to attract early HMRC scrutiny are:
Businesses with significant CBAM import volumes that have not registered by 1 January 2027
Businesses that have registered but cannot produce contemporaneous evidence of their threshold monitoring process
Businesses that applied the threshold incorrectly — for example, by treating it as a per-commodity threshold rather than an aggregate threshold
Businesses that delegated CBAM compliance entirely to their customs broker without establishing internal oversight or documentation
HMRC scrutiny of new tax regimes frequently focuses on whether the business had appropriate oversight structures in place, not merely whether the arithmetic was correct.
Preparing for the First Reporting Cycle
Registration is the first step in a compliance journey that concludes — for the first time — with the 31 May 2028 return and payment deadline. The transition from registration to reporting requires a fundamentally different data capability: registration needs import values, whilst reporting requires embedded carbon data at the level of specific imported goods, by origin country and production facility. These are two separate data challenges, and the timeline for the second is longer than for the first.
By 1 January 2027, a registered business must have a functioning system for recording the embedded emissions of CBAM goods as they are imported. This requires engagement with overseas suppliers to obtain embedded carbon data in the required format, or the application of default values where supplier-specific data is unavailable. Default values, where confirmed in the final emissions and verification regulations, are likely to differ from supplier-specific data — creating a direct financial incentive for businesses to engage suppliers on actual embedded carbon figures rather than rely on published defaults.
Supplier engagement on embedded carbon data should begin no later than Q4 2026. Overseas suppliers — particularly those providing steel and aluminium — may have limited familiarity with UK CBAM data requirements and may require significant lead time to produce compliant documentation. Businesses that have not begun supplier engagement before 1 January 2027 risk entering the first accounting period without the data needed to prepare an accurate return.
FAQ Section
Q: Who must register with HMRC under the UK Carbon Border Adjustment Mechanism?
A: Any business that imports iron and steel, aluminium, cement, fertilisers, or hydrogen into the UK must register with HMRC as a UK CBAM liable person once its import values cross the £50,000 threshold under either the backward-looking (preceding 12 months) or forward-looking (next 30 days) test. The obligation applies to the importer of record — the entity named on the UK customs declaration — not to customs brokers or freight forwarders acting on their behalf. Electricity imports are excluded from UK CBAM scope.
Q: How do I determine whether my business has crossed the £50,000 threshold when imports come through multiple suppliers and customs brokers?
A: The threshold is assessed against the aggregate customs value of all CBAM-covered goods imported, regardless of how many suppliers or customs brokers are used. Consolidate your customs declaration data — drawing on HMRC Customs Declaration Service records and customs broker reports — and aggregate the declared values for all CBAM-covered commodity codes across all entry points. The practical step is to extract 12 months of import data from your customs declarations, filter for CBAM commodity codes, and sum the declared values.
Q: What is the difference between the UK CBAM backward-looking test and forward-looking test?
A: The backward-looking test assesses the total customs value of CBAM goods you have already imported over the preceding rolling 12-month period. The forward-looking test assesses whether you expect to import £50,000 or more of CBAM goods in the next 30 days. Both tests run simultaneously and continuously — either test, when met, creates an obligation to register with HMRC within 30 days (or immediately, in the case of the forward-looking test).
Q: How does the forward-looking 30-day test work when future purchase orders change frequently?
A: Base the forward-looking assessment on confirmed purchase orders and shipment schedules at the time of assessment, and retain that data as evidence of the conclusion reached. Published guidance does not specify a documentation standard, but a contemporaneous record of the PO data and the resulting conclusion provides the defensible evidence trail an HMRC enquiry would require. Where the expected value range straddles the £50,000 threshold, treat the test as triggered and register.
Q: What evidence will HMRC expect if it challenges our decision not to register?
A: HMRC would expect a contemporaneous, dated record of both the backward-looking and forward-looking threshold assessments, supported by the underlying customs declaration data and purchase order data used to reach the conclusion. The record should include a commodity code analysis confirming scope, the calculated aggregate import values, and a signed determination by a named responsible officer. An assessment that exists only in institutional memory, or was prepared retrospectively after an HMRC enquiry, will not satisfy the standard.
Q: What should businesses complete before the UK CBAM registration window opens in late 2026?
A: Confirm which imported goods fall within UK CBAM scope; calculate the current backward-looking threshold position using 12 months of customs declaration data; establish a monthly monitoring process for both tests; assign named internal ownership of the registration process; and create a compliance evidence register. Businesses that will clearly exceed £50,000 from 1 January 2027 should register as soon as the HMRC portal opens, without waiting for a formal threshold-crossing event under the live regime.
References and Sources:
This article is backed by authoritative source and research;
HM Treasury / HMRCDocument Title: Factsheet: Carbon Border Adjustment Mechanism (CBAM)Date: 28 November 2025URL: https://www.gov.uk/government/publications/factsheet-carbon-border-adjustment-mechanism-cbam/factsheet-carbon-border-adjustment-mechanism
UK GovernmentDocument Title: Carbon Border Adjustment Mechanism (Policy Summary)Date: 9 April 2026URL: https://www.gov.uk/government/publications/carbon-border-adjustment-mechanism-cbam-policy-summary/carbon-border-adjustment-mechanism-cbam-policy-summary
UK GovernmentDocument Title: Draft Regulations: CBAM Emissions and Verification ConsultationDate: 9 April 2026URL: https://www.gov.uk/government/consultations/draft-regulations-carbon-border-adjustment-mechanism-cbam-emissions-and-verification
UK GovernmentDocument Title: Carbon Border Adjustment MechanismDate: 26 November 2025URL: https://www.gov.uk/government/publications/introduction-of-carbon-border-adjustment-mechanism/carbon-border-adjustment-mechanism
UK GovernmentDocument Title: Government Response to UK CBAM ConsultationDate: 30 October 2024URL: https://assets.publishing.service.gov.uk/media/679cb194a9ee53687470a2fa/Introduction_of_a_UK_Carbon_Border_Adjustment_Mechanism_from_January_2027_-_Government_response_to_the_policy_design_consultation.pdf
European Commission DG TAXUDDocument Title: Carbon Border Adjustment MechanismDate: CurrentURL: https://taxation-customs.ec.europa.eu/carbon-border-adjustment-mechanism_en
European Commission DG TAXUDDocument Title: CBAM Registry and ReportingDate: Updated 2025URL: https://taxation-customs.ec.europa.eu/carbon-border-adjustment-mechanism/cbam-registry-and-reporting_en
European CommissionDocument Title: CBAM Successfully Entered Into Force on 1 January 2026Date: 14 January 2026URL: https://taxation-customs.ec.europa.eu/news/cbam-successfully-entered-force-1-january-2026-2026-01-14_en
Finance Act 2026Document Title: Part 5 — Carbon Border Adjustment MechanismDate: 2026URL: https://www.legislation.gov.uk/ukpga/2026/11/part/5
Legal Disclaimer:
This article is provided for general informational and educational purposes only and does not constitute legal, tax, regulatory, or professional advice. While CBAM Journal strives to ensure accuracy using authoritative sources, regulations and guidance may change over time. Readers should seek independent professional advice before making compliance or business decisions based on the information contained in this article. For full terms, limitations of liability, and additional disclosures, please see our Disclaimer page: https://www.cbamjournal.com/disclaimer
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