The Most Common UK Customs Declaration Errors and How to Fix Them

Here is something most businesses don't fully appreciate: when your freight forwarder submits a customs declaration to HMRC, it is submitted on your behalf, and you, not the forwarder, are legally responsible for its accuracy.

HMRC can audit your customs records up to four years after a shipment clears. If errors are found, whether they were caused by your forwarder, a third-party agent, or your own team, the resulting duty assessments, VAT adjustments, and penalties land with you. The forwarder moves on to the next shipment. You inherit the liability.

The frustrating reality is that the most damaging errors are also the most common. They appear across hundreds of shipments, compounding silently year after year, until an audit brings them all to the surface at once. This guide covers the errors we find most frequently when reviewing client trade data, explains why they happen, and tells you exactly what to do about them.

1. Incorrect Commodity Codes

Every product imported into or exported from the UK must be classified using a 10-digit commodity code from the UK Trade Tariff. These codes determine the rate of import duty, any applicable licences, anti-dumping duties, quota restrictions, and VAT treatment. Getting the code wrong means you are either overpaying duty, a direct financial loss, or underpaying, which creates a retrospective debt.

This is by far the most common error we encounter. The UK Trade Tariff has over 16,000 commodity headings, and many products can plausibly fall under several different codes depending on their composition, intended use, or processing state. Freight forwarders classify hundreds of different products every week and frequently rely on classifications that are 'close enough' rather than rigorously verified.

Why it's dangerous

HMRC actively audits commodity code accuracy. Their systems flag statistical anomalies, if your supplier declares a product under one code for export and you or your agent declare it under a different code for import, that discrepancy is visible to HMRC and can trigger an audit. Additionally, HMRC can issue a customs assessment for the full underpaid duty going back three years, plus interest, plus penalties.

How to fix it

•       Obtain a product-by-product commodity code review from a qualified customs consultant, do not rely on the forwarder's existing classifications without verification

•       For high-value or high-volume products, apply to HMRC for a Binding Tariff Information (BTI) ruling, this gives you legal certainty on the correct code and protects you in an audit

•       Build a classification register for your core product range and share it with every agent and forwarder you use

•       Review your HMRC import data (available free via CHIEF or CDS data downloads) to identify any codes that vary inconsistently across similar shipments

2. Incorrect Customs Procedure Codes (CPCs)

A Customs Procedure Code (CPC) tells HMRC what is happening to the goods, whether they are being released to free circulation, entered into a special procedure (such as a customs warehouse or inward processing), temporarily admitted, or re-exported. Using the wrong CPC can negate a duty relief entitlement or, worse, create a duty liability where none should exist.

Common CPC mistakes

•       Using the standard import CPC (40 00 000) for goods that should be entered into a customs warehouse (71 00 000)

•       Using the wrong CPC for re-exported goods, triggering duty that should have been suspended

•       Using an inward processing CPC without the relevant HMRC authorisation in place

•       Mixing CPCs across shipments in a way that creates an unreconcilable customs account

How to fix it

CPC errors tend to be systemic rather than isolated, if a forwarder has been using the wrong CPC for one type of shipment, they've likely been using it consistently for months or years. A full review of your import declarations for the past 12 months will typically identify patterns. Where errors have already occurred, a voluntary disclosure to HMRC (discussed below) is the appropriate response.

3. Incorrect Customs Value

The customs value of imported goods is the figure on which import duty is calculated. Under UK law, it must be determined using one of six accepted valuation methods, with the transaction value (the price actually paid or payable) being the primary method. Getting this wrong, either under-declaring to reduce duty or over-declaring due to including non-dutiable charges, creates both financial and legal risk.

Common valuation mistakes

•       Including or excluding freight costs incorrectly, Customs Procedure requires cost, insurance, and freight (CIF) value: if you're using FOB Incoterms, freight must be added

•       Declaring the invoice value without adjusting for royalties, assists (tooling or materials supplied to the manufacturer), or related-party pricing adjustments

•       Transfer pricing issues: businesses that import from related companies (subsidiaries, parent companies, joint ventures) must apply specific valuation rules to demonstrate the transaction value is acceptable to HMRC

•       Failing to include buying commissions in the customs value

How to fix it

Commission a customs valuation review for your top 10 imported products by value. This exercise typically takes 2–3 days and will identify whether your current valuations are defensible to HMRC. Transfer pricing cases in particular should be reviewed by a qualified customs consultant, as the consequences of getting this wrong can be significant.

4. Wrong Country of Origin

The origin of goods, not the country they were shipped from, but the country where they were manufactured or substantially transformed, affects the rate of duty applied. Under the UK's network of Free Trade Agreements, goods originating in certain countries can be imported at reduced or zero duty rates. Claiming preferential origin when it isn't justified, or missing the opportunity to claim it when it is, are both costly errors.

The specific risks

•       Claiming UK-EU preference under the UK-EU Trade and Cooperation Agreement (TCA) without adequate proof of origin, HMRC will disallow the preference and assess the full duty

•       Accepting supplier declarations of origin at face value without verifying that the goods actually meet the Rules of Origin (ROO) under the relevant Free Trade Agreement

•       Missing preference claims because your forwarder hasn't been instructed to apply them, leaving money on the table shipment after shipment

•       Incorrectly declaring origin on export declarations, which can expose your overseas customers to penalties in their own customs territory

How to fix it

•       For each country you import from, check whether the UK has a Free Trade Agreement in place (the UK Trade Tariff lists all applicable agreements)

•       For goods you're claiming preference on, obtain and retain valid proof of origin from your supplier — this is a EUR.1 certificate, a supplier's declaration, or an origin declaration on the invoice

•       Conduct a Rules of Origin analysis for your top imported products to confirm they genuinely meet the preferential criteria

5. Errors in Importer of Record

The Importer of Record (IOR) is the entity declared to HMRC as legally responsible for the import. This must be the entity that has title to the goods at the point of import and is liable for any duty. Using the wrong EORI number, for example, your freight forwarder's EORI rather than your own, means the customs debt is legally registered against the wrong entity, creating complications with VAT recovery and liability allocation.

This has become more common since Brexit, as DDP (Delivered Duty Paid) Incoterms arrangements have encouraged some freight forwarders to act as IOR as a service, which creates a complex and sometimes problematic legal arrangement.

How to fix it

Review your import declarations and confirm that your own EORI number appears as the declarant. If your forwarder's EORI has been used, speak to your customs consultant about the implications and the options for correcting the position going forward.

6. Failure to Claim Available Duty Relief

Not every error results in overpayment due to a mistake on the declaration itself. Some of the most significant duty overpayments we identify arise simply from failing to use the reliefs that are legitimately available.

We regularly audit import data for new clients and find:

•       Businesses that have been paying full duty on goods that qualify for Inward Processing Relief, in some cases, for years

•       Manufacturers paying full duty on raw materials when their finished products are exported, making them eligible for IP relief that would have eliminated the duty entirely

•       Businesses storing imported goods in a standard warehouse and paying duty upfront, when a customs warehouse authorisation would have deferred that cost indefinitely

•       Importers paying anti-dumping duties on goods that qualify for exemption

•       Businesses missing preference claims due to incomplete supplier declarations

A real example:  We took on a client in the North West manufacturing sector who had been paying approximately £85,000 per year in import duty on raw materials. After reviewing their supply chain, we identified that their production process qualified for Inward Processing Relief. The duty was avoidable. They had simply never been told.

7. Missing or Incorrect Supplementary Declarations

Businesses using simplified customs procedures are required to submit supplementary declarations within a defined period after the goods arrive. Missing these deadlines or submitting incorrect supplementary declarations generates customs debt and can lead to the simplified procedure authorisation being withdrawn, potentially with significant operational disruption.

8. Inadequate Record-Keeping

This is less an error on a specific declaration and more a systemic risk. HMRC's customs audit process goes beyond checking individual declarations, they assess whether your overall customs record-keeping meets the legal standard. UK law requires importers and exporters to retain customs records for a minimum of four years.

Businesses that cannot produce commercial invoices, packing lists, proof of origin, transport documents, and evidence of duty payment for shipments going back four years are in a vulnerable position if HMRC conducts a compliance check.

What to Do If You've Found Errors

If a review of your customs declarations reveals errors, whether involving underpaid duty, incorrect codes, or missed relief claims, the right approach depends on the nature and scale of the issue.

Voluntary Disclosure

Where duty has been underpaid, making a voluntary disclosure to HMRC before they discover the error themselves is strongly advisable. HMRC's penalty regime for customs errors distinguishes between prompted and unprompted disclosures. An unprompted voluntary disclosure, where you identify and report the error yourself, typically attracts a significantly lower penalty than one that is only raised because HMRC has already found it. In some cases, an unprompted disclosure of a non-deliberate error results in no financial penalty at all, with only the duty and interest to settle.

Overpayment Claims

Where duty has been overpaid, due to incorrect commodity codes, missed preference claims, or valuation errors, you can submit an amendment or claim a refund from HMRC. Claims for overpaid duty can go back up to three years, so a systematic review of your import data is worthwhile even if you suspect only relatively modest errors.

Building a Declaration Error Prevention Routine

The businesses that manage customs declarations well are not those with perfect agents, they are those with robust internal oversight. Regardless of who submits your declarations, you should:

•       Review a sample of your import and export declarations each month against the underlying commercial documents

•       Cross-check commodity codes on new products before the first shipment, not after

•       Brief every freight agent and forwarder you use with a written classification register and instruction sheet

•       Keep a central log of all HMRC authorisations, their conditions, and their renewal dates

•       Have an annual customs compliance review carried out by an independent consultant

The four-year audit window means that errors made today remain a liability until 2029. The cost of proactive mamnagement is a fraction of the cost of a retrospective HMRC assessment.

If you want to find out more, book a free consultancy session with us today.