Customs Duty Calculator

How the figure is built

Customs duty is assessed as customs value × rate, where the rate may be ad valorem (a percentage), specific (an amount per unit, kilogram or litre), or compound (both). Most consumer goods are ad valorem; agricultural products, alcohol and tobacco commonly are not.

Customs value under the WTO valuation agreement is normally the transaction value: the price actually paid or payable: with specified additions such as assists, royalties, and commissions other than buying commissions.

A real example

The $18,000 shipment at an ad valorem 6.5% on an FOB basis: $1,170.

Now a specific duty instead, say $0.85 per unit. On 1,000 units that is $850, and it is unaffected by the price. If the same goods were bought at $12 rather than $18, the ad valorem duty would fall to $780 and the specific duty would stay at $850.

Specific duties therefore hit cheap goods hardest as a percentage. At $12 a unit the specific duty is 7.1% of value; at $30 a unit it is 2.8%. That regressive shape is deliberate in most schedules where it appears.

The usual mistakes

The transaction value is not always the invoice price. Tooling paid for separately, materials supplied free to the manufacturer, design work done outside the country of import, and royalties tied to the goods can all be dutiable additions, and omitting them understates the value.

Related-party transactions are also scrutinised. Where buyer and seller are connected, customs may reject the transaction value if the relationship influenced the price, and fall back to a different valuation method entirely.

Using the result

List every payment connected to the goods and check each against the dutiable additions rules before declaring. Assists and royalties are the two that most often catch importers out, and both are found in the accounts rather than on the commercial invoice.

Then keep the supporting documentation for the statutory retention period, commonly five to seven years. Customs audits look backwards, and a valuation that cannot be evidenced is treated as understated.

Binding rulings and why they are worth the trouble

Most customs authorities issue advance rulings on classification, valuation or origin, binding on the authority for a period of years. They are typically free or inexpensive and take a few weeks.

The value is certainty. A ruling removes the risk that a code accepted for three years is challenged at audit with retrospective duty on every entry since, which is the scenario that turns a classification question into a business-threatening one.

They are worth seeking wherever the classification is genuinely ambiguous, where the duty difference between plausible codes is material, or where the volume is large enough that a retrospective correction would hurt. For a business importing one product line at scale, a ruling is one of the highest-return hours of administration available, and the request itself forces the kind of precise description of the goods that makes the right code obvious.

The commercial invoice has to describe the goods well enough for classification, state the terms of sale, and show the country of origin. Vague descriptions are the most common cause of clearance delays.

A supplier writing "samples" or "gift items" on a commercial shipment creates a query at best and a valuation challenge at worst, and it is worth specifying the invoice format with a supplier before the first order rather than correcting it afterwards.