How customs duty is calculated

The rates below are invented for illustration, so don't use them for real goods. All amounts are in euros.

Most manufactured goods are ad valorem. Agricultural lines are where you'll meet specific, compound and mixed rates. The WTO's jargon buster separates the last two: compound rates add the two components, while mixed rates apply one or the other depending on a limit. A specific rate also gets heavier as prices fall, because the amount stays fixed while the value drops.

A tariff quota sets a lower rate for a limited volume and a higher rate above it. Say 10,000 kg of a quota are available, 8,000 kg are used, and you enter 3,000 kg at 4 per kg:

• 2,000 kg in quota: 2,000 x 4 x 5% = 400.00
• 1,000 kg out of quota: 1,000 x 4 x 25% = 1,000.00
• Duty: 1,400.00

Quotas usually fill on a first-come basis or by licence. Check how much is left on the day, not when you place the order.

Under the WTO Valuation Agreement, the start point is the price paid or payable, adjusted for commissions, packing, assists and royalties. Whether freight and insurance go in is left to each member. Take goods at 10,000 with 1,200 freight, at a 5% rate:

The bases by country are on the landed cost page. Carrier surcharges for peak season, security and war risk count in the UK value when they relate to the journey before arrival, which people often miss.

A line in a tariff has several rates. Most importers look at the general (MFN) rate first, then a preferential rate if their goods qualify under a trade agreement. Preference is a claim you have to make and prove. Country of origin isn't the country you shipped from.

Some countries then add duties on top based on origin or product: anti-dumping duties, safeguards, and in the US, Section 232 and Section 301 duties. In the US, these extras usually apply to the same dutiable value as the base rate. The note to chapter 99 for the July 2026 Section 301 duties says goods stay subject to the general rate as well, and that an FTA claim doesn't remove the additional duty unless a specific exemption says so.

Example, our own illustration, at rates as of 5 November 2026. Cotton kitchen towels from Vietnam entered in the US at $20,000, with an assumed general rate of 9.1% and the 12.5% Section 301 duty:

• General rate: $20,000 x 9.1% = $1,820.00
• Section 301: $20,000 x 12.5% = $2,500.00
• Duty: $4,320.00, an effective 21.6%

Current US measures are on US tariff changes.

Valuation adjustments, a changed classification, a rejected origin claim or a retrospective anti-dumping review can all change duty after release. Keep the workings with the entry. Then use the import duty calculator for a real code, and the HS code classifier if you're not sure of the code yet.