Guides / Customs mistakes and penalties · Updated 30 September 2026

Customs declaration mistakes, corrections and penalties in the UK

Wrong codes, values, origin claims and CPCs are the usual causes of customs penalties. Here is how HMRC expects you to correct them, and how disclosure affects any penalty.

This guide is also available in Polish.

Most customs penalties in the UK do not start with smuggling. They start with an ordinary declaration that contains a wrong code, a wrong value or a preference claim nobody could support. HMRC runs a civil penalty regime for these contraventions, and it also gives traders formal routes to put mistakes right. Knowing both sides of that system is the cheapest compliance tool you have.

The mistakes that cause most trouble

Wrong commodity code

The commodity code decides the duty rate, whether import controls apply and which data the declaration needs. A wrong code can mean underpaid or overpaid duty. HMRC's own amendment guidance singles this case out: where an incorrect commodity code has led to an underpayment or overpayment, the ordinary post-clearance amendment route is not used, and the case goes to the C18 team or the repayment process instead. If you are unsure of a classification, an Advance Tariff Ruling is the formal way to get certainty before you ship.

Wrong customs value

Leaving out freight and insurance to the UK border, royalties, assists or other elements of the price, or declaring a value that does not match the commercial reality, changes both duty and import VAT. The valuation methods guide explains what should be included.

Wrong origin or preference claim

Claiming a preferential rate under a trade agreement without the evidence to back it is an incorrect declaration like any other. If the claim fails, the full duty becomes due and the error is treated in the same way as other declaration inaccuracies.

Wrong customs procedure code

The CPC tells HMRC what regime the goods are entering, such as free circulation, a relief or a special procedure. Notice 301 lists unauthorised use of customs procedures, including incorrect drawback claims, among the contraventions the civil penalty regime covers. Our guide to customs procedure codes covers the common ones.

Missing licences

Licensing is different. HMRC's Notice 301 says breaches of prohibitions, restrictions and licensing requirements are excluded from the civil penalty regime and remain under criminal provisions. That makes a missing licence a more serious problem than a coding error, not a lesser one.

Correcting a declaration

According to HMRC's guidance for the Customs Declaration Service:

Before clearance you can amend a declaration through your CDS software, as long as it has not been cleared and you have not received the final tax calculation message.
After clearance you contact HMRC to review the change. You have up to 3 years from acceptance of the declaration to amend it, and 90 days to cancel it.
Some fields, such as certain previous documents, reference numbers, delivery terms and some valuation fields, do not need HMRC notification; you record the change in your own commercial records.

If you paid too little

Underpayments on CDS declarations are disclosed through a voluntary clearance amendment (form C2001), made online with a Government Gateway login. You provide the original and revised procedure codes, the commodity code details and movement reference number, importer and representative details and the amounts involved. HMRC then raises a C18 demand for the extra duty or VAT. If you use postponed VAT accounting, underpaid import VAT is corrected on your VAT Return instead.

If you paid too much

Overpayments are reclaimed through CDS or, for private individuals, people without an EORI number and those who are not VAT registered, through online form C285. HMRC's time limits are 3 years for standard overpayments, 1 year for rejected imports and 90 days where an import declaration is withdrawn. HMRC aims to decide within 30 days and repays only to a UK bank account.

How the civil penalty regime works

Customs civil penalties come from sections 24 to 41 of the Finance Act 2003 and the Customs (Contravention of a Relevant Rule) Regulations 2003. The Regulations' Schedule lists each relevant rule, the person liable and the maximum penalty. Regulation 3(7) adds that if a contravention continues after HMRC has given written notice, the continuation counts as a further contravention.

In practice, Notice 301 describes a stepped approach:

Most contraventions first get a warning letter. A similar contravention within 2 years can then lead to a financial penalty.
A penalty can be issued for a first contravention where the error is serious, where HMRC's written guidance was ignored, or where the conditions of an authorisation were breached.
Notice 301 gives a maximum of £2,500 per contravention for serious irregularities and £1,000 for others, and describes penalties typically starting at £250 and rising in steps for repeated errors.
HMRC must issue a penalty within 3 years of the contravention, or within 2 years of having enough facts, according to the notice.

A written disclosure made before HMRC starts enquiring is treated very differently from an error HMRC finds first. Act as soon as you spot a mistake.

Why disclosure matters

Notice 301 is clear that a written disclosure made before HMRC enquires into the customs duty issue prevents a penalty being imposed, and it names the C18 Team at the National Clearance Hub as the place to send it. HMRC can also reduce a penalty, even to nil, for mitigating circumstances, taking account of what led to the error, your compliance history and the remedial action you took. Good faith, a small tax loss and inability to pay are specifically not mitigating factors.

A reasonable excuse, such as a computer breakdown you acted promptly to fix, can remove liability altogether. Relying on a third party whose conduct caused the error is not a reasonable excuse, which matters if you use an agent. Under direct representation the importer stays liable; under indirect representation the agent is jointly liable.

A short prevention checklist

Check commodity codes against the product, not the supplier's invoice description.
Build the customs value from the full transaction, including transport to the UK border.
Only claim preference when you hold the origin evidence at the time of import.
Confirm the CPC matches the regime you actually intend to use.
Check licensing and restrictions before shipping, since these fall outside the civil regime.
When you find a mistake, correct it in writing through the right channel before HMRC asks.

For worked examples from the UK–Poland trade lane, Plutos keeps a practical list of customs errors that lead to penalties. If you get a penalty you disagree with, Notice 301 says you can ask for a review within 30 days and then appeal to the independent tax tribunal.

Related guides

More examples of costly customs errors

Plutos is a UK–Poland customs information site run by the same team as Easy Clearance. Its article walks through the errors that most often lead to penalties.

Read the Plutos article

Sources

General information, not legal, tax or customs advice. Rules change; confirm current requirements on gov.uk or with a registered agent before you ship.