How to calculate duty? Simple formula [2026]

TL;DR

Quick definition

Duty is calculated on the customs value, which usually combines the goods value with transport costs up to the border. Once the duty amount is known, VAT is then calculated on the enlarged base, so mistakes in the first step affect the whole landed cost. A reliable estimate therefore depends on correct valuation, the right commodity code and a clear view of which charges belong in the customs base.

The basis for customs duty calculation is Customs Value. Customs Value = Invoice Price of Goods + Transport Cost to the EU (or UK) border.

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Template: `Customs Duty = Customs Value × Duty Rate (%)` Example:

You buy shoes from China for 1000 PLN.
Transport costs 200 PLN.
Customs duty on shoes (from China) is e.g. 8% (fictional).

Customs base: 1200 PLN. Duty payable: 1200 × 0.08 = 96 PLN.

What about VAT? VAT is calculated on the total sum (Goods + Transport + Duty). VAT base: 1200 + 96 = 1296 PLN. VAT (23%): 1296 × 0.23 = 298.08 PLN.

Total payable at the border: 394.08 PLN.

What the current official guidance means in practice

For operational work, the current procedural rules, declaration fields and relief conditions should be checked directly against the official guidance. For this topic, the core reference points are GOV.UK / HMRC, European Commission.

Operational watch-outs

Most delays come from inconsistent data between the commercial invoice, packing list, tariff classification, reference numbers and transport assumptions. Before shipment release, confirm who is responsible for clearance, whether the data set is complete and when the declaration must be filed.

Documents and data to prepare

The minimum working pack worth preparing before speaking to customs support or filing a declaration includes:

commercial invoice with a complete goods description
packing list with quantities, weight and package count
HS/CN code and origin information
EORI number and the party responsible for the declaration

Practical notes for UK-PL operators

For regular flows, keep a stable data template: goods description, HS code, origin, Incoterms, carrier details and source documents. This shortens response time and reduces border corrections.

Official sources

UK GOV (Import VAT & PVA) — GOV.UK / HMRC, 2026-03-04
EU Commission (Customs procedures) — European Commission, 2026-03-04
GOV.UK: tax and duty on goods sent from abroad — GOV.UK / HMRC, 2026-03-04

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