The first UK CBAM return is due before the end of May 31, 2028, and it covers a single 12-month accounting period running from January 1 to December 31, 2027. Payment of the CBAM charge for that period is due by the same date. Accounting periods turn quarterly from January 1, 2028, so the second return, for January to March 2028, is due July 31, 2028.
Reporting applies to a business that has triggered registration: it imported CBAM goods worth £50,000 or more in the preceding 12 months, or expects to import that value within 30 days (Finance Act 2026, Schedule 17, paragraph 2(2)). The tax covers 5 sectors: aluminium, cement, fertilisers, hydrogen, and iron and steel (section 143(3)). Part 5 of the Finance Act 2026 is the legal basis, and the UK CBAM guide explains the charge itself.
As of October 12, 2026, the reporting law is made but the filing system is not open. Three instruments set the detail from January 1, 2027: SI 2026/802 (Administrative Provisions), SI 2026/830 (Transitory Provision) and SI 2026/995 (Emissions and Verification). HMRC guidance says registration "will open by 1 January 2028", and HMRC has published no return form or return service.
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What Must a UK CBAM Return Contain?
A UK CBAM return must give 7 items of information for each CBAM good imported in the accounting period on which CBAM is charged, plus a confirmation that the return is true and accurate. Regulation 10 of SI 2026/802 sets the list. Regulation 17(3) of SI 2026/995, made on September 8, 2026, inserted items (e) to (g).
The table below sets out each return field, its legal source, where the data comes from, and whether the figure must be verified.
| Field | What it covers | Source of the data | Verified figure required |
|---|---|---|---|
| 8-digit commodity code, reg 10(1)(a) | The code of each CBAM good | Import declaration; Schedule 16 to the Finance Act 2026 | No |
| Weight, reg 10(1)(b) | Net weight in kilograms, without packing, at the time of import (reg 4) | Import declaration, commercial invoice, packing list | No, but HMRC can determine the weight itself (reg 12) |
| Carbon price relief, reg 10(1)(c) | The amount of relief claimed, in sterling | Effective carbon price calculation under SI 2026/809 | Yes: a carbon pricing verification form completed by an accredited verifier |
| Place of origin, reg 10(1)(d) | Non-preferential customs origin (reg 9) | Proof of origin | No |
| Default value level, reg 10(1)(e) | The default value used, where the importer relies on one | Treasury notice under Schedule 17, paragraph 11(1) | No |
| Emissions intensity, reg 10(1)(f) | Tonnes of CO2 equivalent per tonne of good, where actual data are used | Verified emissions data from the producing installation | Yes: verified by a verifier meeting regulation 12 of SI 2026/995 |
| UK-origin input, reg 10(1)(g) | Whether the good was produced from another CBAM good of UK origin (section 147(3)) | Supplier production and origin records | No |
| Confirmation of accuracy, reg 10(2) | A statement that the return is true and accurate to the best of the filer's knowledge | The person making the return | Not applicable |
Two further requirements come from HMRC documents, not from the regulations, and the first is still a draft.
- Quarter of import (draft): HMRC's draft force of law notice under regulation 10(3) requires the first return to state the quarter in which each CBAM good was imported. The notice has no legal force until January 1, 2027.
- Consignment-level lines (policy): HMRC's Policy Summary, updated September 9, 2026, says multiple consignments of the same CBAM good are reported separately, as are different CBAM goods in one shipment.
A return filed on default values cannot be switched to actual emissions data afterwards. Paragraph 8 of Schedule 17 allows a return to be amended only to correct an error, and paragraph 8(2) bars an amendment that replaces default values with actual emissions data. No default values notice appeared on the gov.uk CBAM collection as of October 12, 2026; HMRC's July 2026 guidance said the values would be set "later this year". The UK CBAM default values page tracks that notice.
The UK CBAM Reporting Timetable
UK CBAM reporting runs on 1 annual accounting period for 2027, then on quarterly accounting periods from January 1, 2028, with the return and the payment due on the same date. The standing rule is the last working day of the second month after the accounting period ends (Schedule 17, paragraphs 6(3) and 7(2)). SI 2026/830 sets longer, fixed deadlines for the first 3 accounting periods.
The table below lists every reporting date fixed so far, in date order.
| Date | Obligation | Period covered | Legal basis |
|---|---|---|---|
| January 1, 2027 | CBAM is charged on imports; record keeping begins | Goods imported on or after this date | Finance Act 2026, section 158(1); SI 2026/802, reg 5 |
| January 31, 2028 | Register, where registration was triggered in 2027 | Not applicable | Schedule 17, paragraph 2(4), as modified by SI 2026/830, reg 2(2) |
| May 31, 2028 | First return and payment | January 1 to December 31, 2027 | Schedule 17, paragraphs 6 and 7, as modified by SI 2026/830, reg 2(3) and (4) |
| July 31, 2028 | Return and payment | January 1 to March 31, 2028 | Same |
| September 29, 2028 | Return and payment | April 1 to June 30, 2028 | Same |
| November 29, 2028 on the statutory wording; HMRC lists November 30 | Return and payment | July 1 to September 30, 2028 | Schedule 17, paragraphs 6(2), 6(3) and 7(2), unmodified; section 155(1); Banking and Financial Dealings Act 1971, Schedule 1, paragraph 2 |
| February 28, 2029 | Return and payment | October 1 to December 31, 2028 | Schedule 17, paragraphs 6(2), 6(3) and 7(2), unmodified |
HMRC's Policy Summary lists the same return dates with 1 exception: it gives November 30, 2028 for the July to September 2028 period. Section 155(1) excludes from "working day" any day that is a bank holiday in any part of the United Kingdom under the Banking and Financial Dealings Act 1971, and paragraph 2 of Schedule 1 to that Act makes November 30 a bank holiday in Scotland when it falls on a weekday.
November 30, 2028 is a Thursday, so on the statutory wording the last working day of the month is Wednesday, November 29, 2028. That date is cbamguide.com's calculation, not an HMRC statement, and HMRC had not addressed the difference as of October 12, 2026. Filing and paying by November 29 satisfies both readings. Registration triggers and pre-2027 milestones sit on the UK CBAM deadlines page.
The First Annual Return for the 2027 Accounting Period
The first return covers 12 months and is due 5 months after the period ends. HMRC's Policy Summary gives the reason: "This is to provide businesses with sufficient time to obtain supporting information required to complete their first return, whilst also allowing HMRC time to develop and test necessary IT systems."
One annual return still holds 4 quarters of pricing: the charge uses the sectoral price for the quarter in which liability is incurred (section 149(2)), which explains the draft requirement to state the quarter of import. Verified emissions data for 2027 imports can come from the year of import, the preceding year, or the year of production (SI 2026/995, regulation 9(2)).
The Move to Quarterly Returns
Quarterly accounting periods end in March, June, September and December (Schedule 17, paragraph 6(2)). The first 2 quarterly returns keep longer filing windows, of 4 months and 3 months, before the 2-month rule applies from the July to September 2028 period.
A return is due for every accounting period while a business is registered or registrable, including a period with no CBAM to pay. HMRC can amend accounting periods and deadlines by regulations under paragraph 9 of Schedule 17, so dates beyond February 2029 follow the standing rule unless amended. CBAM Brief (EUR 199 a month) sends email alerts when CBAM deadlines, default values, CN codes and certificate prices change.
How to File a UK CBAM Return
A UK CBAM return is filed online through HMRC's CBAM service, accessed with a Government Gateway account, by the liable person or by a tax agent the liable person appoints. The online route sits in a draft force of law notice under paragraph 7(4) of Schedule 17, which takes effect on January 1, 2027; the tax agent option comes from HMRC's Policy Summary. As of October 12, 2026, the service is not open.
The liable person is the importer, and liability does not pass to a customs broker or tax agent acting for the importer. Section 146 of the Finance Act 2026 defines the importer as the person in whose name the customs declaration is made or, where it is made on behalf of another person, the person on whose behalf it is made. HMRC's Policy Summary adds: "The tax agent cannot register for CBAM on behalf of the liable person and no liability will be attached to the tax agent." Firms that state a UK CBAM offer, from tax advisers to customs brokers, are listed by type and scope in the directory of UK CBAM services.
The 7 steps to file a UK CBAM return are listed below.
- Confirm that you are the importer under section 146, using your import declarations.
- Test the £50,000 threshold on the first day of each month and whenever a large order is expected.
- Register your business yourself through the CBAM service, since an agent cannot complete this step.
- Collect the 7 return items for every consignment, by 8-digit commodity code and in kilograms.
- Choose default values or verified actual emissions before filing, since a return filed on default values cannot be amended to actual data later.
- Submit the return through the CBAM service, or authorise a tax agent to submit it.
- Pay the charge by the same deadline. The draft notice lists Direct Debit, online banking, telephone banking and credit or debit card.
Registering for the Service
Registration comes before the first return, and the importer registers itself. A business has 30 days from the day it first triggers registration (Schedule 17, paragraph 2(4)); a business that triggers registration in 2027 has until January 31, 2028 (SI 2026/830, regulation 2(2)). HMRC's registration check guidance, published July 16, 2026, states: "Registration for CBAM will open by 1 January 2028." HMRC's main CBAM collection page says it "will open on 1 January 2028", and neither page gives an earlier opening date.
Regulation 7 of SI 2026/802 lists 9 items of registration data, including the EORI number, the date registration was triggered, and the estimated weight of CBAM goods per sector for the following 12 months. The 2 threshold tests are explained on the UK CBAM registration page. Liability does not wait for registration: Schedule 17 applies to a "registered or registrable person", so the first return covers imports from the trigger date.
What Records to Hold Before You File
Six record sets support a UK CBAM return, and the first applies to every business that imports CBAM goods, registered or not.
- Goods records: 8-digit commodity code and description, import date, value and weight (SI 2026/802, regulation 5).
- Exemption evidence: proof that section 147(2) applies, for example UK origin or returned goods relief (regulation 5(e)).
- Registration evidence: records supporting the information given at registration (regulation 8).
- Origin evidence: records showing the place of origin of each good on a return (regulation 11).
- Verification report: the report, or good-specific verification summary, behind an actual emissions intensity (SI 2026/995, regulation 16).
- Carbon pricing verification form: the completed form behind a carbon price relief claim (HMRC record-keeping guidance).
Records are preserved in writing for 6 years beginning with the day after the accounting period ends (SI 2026/802, regulation 6). Records for the 2027 accounting period therefore run to December 31, 2033.
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What Happens If a UK CBAM Return Is Late or Wrong
A late or inaccurate UK CBAM return falls under HMRC's existing tax penalty regimes, which Part 11 of Schedule 17 to the Finance Act 2026 extends to CBAM; the Act contains no per-tonne CBAM penalty. HMRC had not published CBAM-specific penalty guidance as of October 12, 2026. The figures below are read from the legislation as shown on legislation.gov.uk on that date.
Late Filing and Late Payment
The table below shows the consequences of filing, paying or registering after the due date.
| Failure | Consequence | Escalation | Basis |
|---|---|---|---|
| Return made late | 1 penalty point | £200 penalty once points reach the maximum: 2 for an annual return group, 4 for a quarterly group. Each further late return costs £200 | Finance Act 2021, Schedule 24, paragraphs 5 and 15; Schedule 17, paragraph 35 |
| CBAM paid late | No penalty where it is paid in full within 15 days | 3% of the amount unpaid at day 15, a further 3% of the amount unpaid at day 30, then 10% a year on the unpaid balance | Finance Act 2021, Schedule 26, paragraphs 4, 5 and 8; Schedule 17, paragraph 37 |
| CBAM paid late | Late payment interest | Runs until the charge is paid | Finance Act 2009, section 101, in force for CBAM from January 1, 2027 (SI 2026/994) |
| Registration late | Penalty of 30% of the potential lost revenue | 70% where deliberate, 100% where deliberate and concealed; reductions apply for disclosure | Finance Act 2008, Schedule 41, paragraphs 6 and 13; Schedule 17, paragraph 34 |
Regulation 3 of SI 2026/830 places the 2027 return in the annual group and the 2 returns for January to June 2028 in the quarterly group. HMRC has not said how points carry from one group to the other for CBAM; paragraphs 9 to 13 of Schedule 24 hold the general rule.
A reasonable excuse removes a point or a penalty, but reliance on a broker or agent counts only where the importer took reasonable care to avoid the failure (Schedule 24, paragraph 19).
Inaccurate Returns and HMRC Assessment
The table below shows how HMRC treats an incorrect return, a missing return and missing records.
| Failure | Consequence | Escalation | Basis |
|---|---|---|---|
| Careless inaccuracy in a return | Penalty of 30% of the potential lost revenue | 70% where deliberate, 100% where deliberate and concealed; reductions apply for disclosure | Finance Act 2007, Schedule 24, paragraph 4; Schedule 17, paragraph 36 |
| Wrong weight, or no weight record | An HMRC officer determines the weight, using estimates and comparisons with similar goods | CBAM is charged on the determined weight | SI 2026/802, regulation 12 |
| No return, or an incomplete or incorrect return | HMRC assesses the CBAM due, to the best of its judgement where the amount cannot be ascertained | Assessment possible up to 4 years after the accounting period ends, or 20 years for deliberate loss or failure to register | Schedule 17, paragraphs 20 and 24 |
| Records not kept or preserved | £500 penalty | Reasonable excuse defence | Schedule 17, paragraphs 39 and 40 |
| Registration details not updated within 30 days | £500 penalty | £40 for each further day | Schedule 17, paragraphs 4 and 38 |
| Fraudulent evasion | Criminal offence | Up to 14 years' imprisonment on indictment | Finance Act 2026, Schedule 18, paragraph 1 |
An agent's error remains the importer's error. Paragraph 18 of Schedule 24 to the Finance Act 2007 makes a taxpayer liable where a careless inaccuracy sits in a document given to HMRC on its behalf, unless the taxpayer took reasonable care to avoid it. HMRC must offer a review of an appealable decision, the importer has 30 days to accept, and appeals go to the tribunal (Schedule 17, paragraphs 48, 49 and 57).
How UK CBAM Reporting Differs From EU CBAM Declarations
The UK requires a return and payment of a tax charge to HMRC, while the EU requires an annual CBAM declaration and the surrender of CBAM certificates by September 30, 2027 for 2026 imports. The instruments differ, the dates differ, and nothing filed in one regime discharges the other.
The EU filing is lodged in the CBAM Registry by an authorised CBAM declarant, and the CBAM declaration guide covers it step by step. The EU CBAM guide explains the EU regime as a whole. The table below compares the 2 filings on 7 points.
| Point | UK CBAM | EU CBAM |
|---|---|---|
| What is filed | A CBAM return | A CBAM declaration |
| Who files | The importer (liable person) or its tax agent | The authorised CBAM declarant |
| Frequency | Annual for 2027, quarterly from 2028 | Annual |
| First deadline | May 31, 2028, for 2027 imports | September 30, 2027, for 2026 imports |
| Payment mechanism | Tax paid to HMRC by the return deadline | CBAM certificates, on sale from February 1, 2027, surrendered with the declaration |
| Verification requirement | Only where actual emissions or carbon price relief are reported | Only where actual emissions are declared |
| Retention period | 6 years from the day after the accounting period ends | Until the end of the 4th year after the declaration year |
Pricing differs as well. For 2026 imports the EU side uses the official quarterly certificate price, EUR 82.32 per tonne of CO2 equivalent for Q3 2026, published October 5, 2026. No UK CBAM rate had been published as of October 12, 2026.
Filing in Both Regimes in the Same Year
A business importing into both markets meets 6 filing dates across 2027 and 2028. The EU declaration for 2026 imports is due September 30, 2027. The UK return for 2027 follows on May 31, 2028, then UK quarterly returns on July 31, September 29 and November 29, 2028 (HMRC lists November 30). The September 29 return falls 1 day before the EU's September 30, 2028 deadline for 2027 imports.
Can One Data Set Support Both Filings?
Partly. The EU CBAM data requirements and the 7 UK return items overlap on commodity code, weight, origin and emissions intensity, and HMRC's Policy Summary says the UK monitoring and verification methods "are broadly designed to support interoperability with the EU CBAM". The CBAM data requirements page lists the EU data points to start a supplier request from.
Three UK-specific points still need separate treatment.
- Boundaries: emissions follow HMRC's System Boundaries Document, version 1.00 dated July 10, 2026, not the EU implementing regulations.
- Precision and units: emissions intensity is rounded to 5 decimal places, and weight is reported in kilograms.
- Verifier: the verifier must be independent of the importer and the installation, and accredited for the type of good (SI 2026/995, regulation 12).
Frequently Asked Questions About UK CBAM Reporting
The 7 answers below cover first dates, filing frequency, agents, nil returns, records, amendments and late registration for UK CBAM returns.
When is the first UK CBAM return due?
Before the end of May 31, 2028. The return covers the accounting period January 1 to December 31, 2027, and payment is due on the same date (Schedule 17, paragraphs 6(3) and 7(2) of the Finance Act 2026, as modified by SI 2026/830).
Do I file UK CBAM returns quarterly or annually?
Both, in sequence: 1 annual return for 2027, then quarterly returns starting with the January to March 2028 period. The UK CBAM rate is set per quarter and per sector, so even the annual return records the quarter of import; the UK CBAM rate page explains the calculation.
Can my customs broker file my UK CBAM return for me?
A tax agent can submit returns for you, but cannot register for you, and the liability stays with you as the importer. A broker who completes the import declaration on your behalf does not become the liable person (Finance Act 2026, section 146).
Does a nil return apply below the £50,000 threshold?
No return is due from a business that is neither registered nor registrable, because CBAM is not charged on its imports (section 147(1)(a)); it still keeps goods records under regulation 5 of SI 2026/802. A registered business with nothing to pay files a return for every accounting period until HMRC deregisters it.
How long must I keep UK CBAM records?
For 6 years beginning with the day after the end of the accounting period, or 6 years from creation for a record not tied to a period (SI 2026/802, regulation 6). EU CBAM record keeping runs to a different limit, the end of the 4th year after the declaration year, set out in the CBAM record keeping guide.
Can I amend a UK CBAM return after filing?
Yes, to correct an error only (Schedule 17, paragraph 8). HMRC's draft notice sets a limit of 3 years from the end of the accounting period, and an amendment cannot swap default values for actual emissions data.
What if I registered late for UK CBAM?
You still owe the CBAM charged from the date you triggered registration, and your first return must include those imports. HMRC can register you compulsorily (Schedule 17, paragraph 2(7)), assess the tax due (paragraph 20), and charge a failure-to-notify penalty under Schedule 41 to the Finance Act 2008.
Late registration is 1 of several UK CBAM compliance failures with its own penalty. The UK CBAM compliance guide sets out the full sequence from scope check to payment.
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