How to Prepare Customs Documents for UK Import — Complete Checklist

Importing goods into the United Kingdom after Brexit involves a set of mandatory customs documents that every carrier, freight forwarder and importer must submit correctly and on time. Mistakes in paperwork are the single biggest cause of delays at the UK border — and delays cost money. This guide covers every document you need, when to submit it, and what to watch out for.

Why Customs Documentation Matters More Than Ever

Before Brexit, goods moving between Poland and the UK travelled under EU free circulation rules — no customs declarations required. Since 1 January 2021, every commercial shipment crossing the UK border needs a full customs declaration. For carriers who previously never touched a customs form, the learning curve has been steep.

The UK operates its Customs Declaration Service (CDS) — the central system where all import and export entries are lodged. Understanding which documents feed into a CDS declaration is essential whether you handle customs in-house or work with an agent.

Core Documents Required for UK Import

1. Commercial Invoice

The invoice is the foundation of every customs declaration. It must show:

• Full name and address of seller and buyer
• Description of goods (precise enough to assign a commodity code)
• Quantity, unit price and total value in the transaction currency
• Country of origin
• Incoterms (e.g. DAP, DDP, CPT)

Vague descriptions like “various goods” or “spare parts” will trigger queries from HMRC and delay clearance.

2. Packing List

Where the invoice shows value, the packing list shows physical content: number of packages, gross and net weight per package, dimensions and any special handling markings. HMRC customs officers use it to verify the consignment against the declaration.

3. CMR Consignment Note

For road transport, the CMR note is the contract of carriage between the sender, carrier and consignee. Box 8 (customs) and Box 13 (arrival date) are particularly scrutinised during border checks. Always carry the original signed CMR with the vehicle.

4. EORI Number

Both the importer and exporter need an EORI (Economic Operators Registration and Identification) number. UK importers need a GB EORI; Polish exporters need an EU EORI. Without an EORI the declaration cannot be lodged. If your EORI is new, allow 48 hours for it to activate in HMRC systems before your first shipment.

5. Commodity Code (HS/UK Trade Tariff)

This is not a physical document but a 10-digit code that every import declaration requires. The wrong code can mean the wrong duty rate or triggering a prohibited goods alert. Use the UK Trade Tariff to verify codes before lodging.

6. Import Declaration (Entry Summary)

The full import declaration is lodged in CDS. Your customs agent or in-house declarant will use the above documents to complete it. The declaration generates a Movement Reference Number (MRN) which the driver presents at the border and which links all documents together in the system.

7. ENS — Entry Summary Declaration

The ENS (pre-arrival safety and security declaration) must be submitted to UK customs before the vehicle departs from the EU. For road transport the deadline is at least 1 hour before arrival at the UK port. The ENS generates a DUCR and, once processed, a Safe and Sound (S&S GB) notification. Carriers without a valid ENS are refused entry at the port.

8. Proof of Origin (EUR.1 or REX)

If your goods qualify for preferential tariff treatment under the UK-EU Trade and Cooperation Agreement (TCA), you can avoid import duty. To claim preference you need either a EUR.1 movement certificate or a supplier’s declaration with a REX statement of origin. Origin rules are product-specific — incorrect claims trigger post-clearance audits and duty demands.

Licences, Permits and Additional Certificates

Certain product categories require additional documentation:

• Food and animal products: Health certificate, veterinary inspection, CITES permit (if applicable)
• Plants and plant products: Phytosanitary certificate
• Chemicals: Safety Data Sheet, REACH compliance statement
• Firearms, weapons: Import licence from the Home Office
• Medicines and medical devices: MHRA authorisation

Common Document Errors and How to Avoid Them

Using a Customs Agent vs. Doing It Yourself

Smaller importers often find that the cost of mistakes far exceeds the agent’s fee. A qualified customs broker handles declaration lodging, tariff classification, duty calculation and communication with HMRC on your behalf. They also carry professional indemnity insurance against errors.

If you’re importing regularly on the PL-UK corridor, easyclearance.pl has published a comprehensive customs documents checklist specifically for Polish companies trading with the UK, covering every required form with practical field-level guidance. Their team operates 24/7 and handles time-critical ENS and GMR submissions for road carriers.

Key Takeaways

• Every UK import needs: commercial invoice, packing list, CMR (road), EORI, commodity code, import declaration and ENS
• Origin documents (EUR.1 / REX) are optional but save significant duty costs under the TCA
• Late or incorrect ENS is the most common cause of port delays for road carriers
• Get your commodity codes right before the shipment — not after the border hold
• Working with an accredited customs agent removes risk and ensures HMRC compliance

Last updated: March 2026. UK customs requirements are set by HMRC. Always verify current rules at gov.uk/hmrc.