A duty rate is meaningless until three questions are answered about a shipment. Each is governed by its own body of rules, and each is a common source of disagreement with customs authorities.
Classification decides which rate applies
Every traded good is assigned a code under an internationally harmonised system, with countries adding further digits for their own tariff detail. The code determines the rate.
Classification is often not obvious. Products combining materials or functions can plausibly fall under several headings carrying different rates.
Authorities publish binding rulings that fix the classification of a specific product in advance. Obtaining one removes uncertainty for that importer, though rulings do not bind other countries.
Origin decides which tariff schedule applies
Origin is not simply where a shipment was loaded. It is where the goods were produced or last underwent sufficient transformation, as defined by the applicable rules.
Preferential rates under a trade agreement require the goods to meet that agreement's origin rules, which typically specify a change in classification or a minimum share of local content. Different agreements set different tests for the same product.
Claiming preference requires documentary proof, retained for a defined period and subject to later verification. Failure to substantiate a claim results in duty and often penalties.
Valuation decides what the rate is applied to
Duty is usually charged on the transaction value, meaning the price actually paid. Adjustments add certain costs and deduct others.
Freight and insurance to the border are included in many countries and excluded in others, which produces different duty on identical goods. Royalties and assists may also have to be added.
Where buyer and seller are related, authorities examine whether the price was influenced by the relationship. Alternative valuation methods apply in sequence when transaction value cannot be used.
What else is charged at the same time
Consumption taxes are generally applied at import on the duty-inclusive value, so duty is taxed as well as the goods. Excise applies to specific categories on top.
Trade remedy duties from anti-dumping or safeguard measures are charged in addition to the ordinary rate. These are product and origin specific and change as investigations conclude.
Fees for processing and inspection may also apply. The total landed cost is therefore materially above the headline rate.
Why disputes are common
The three determinations interact, so a change in one alters the outcome of another. Authorities audit after release, sometimes years later.
Importers remain responsible for the accuracy of declarations made on their behalf by agents. Liability is not transferred by using a broker.
Rules, rates and procedures differ by jurisdiction and are revised regularly, so current guidance rather than precedent is the reliable reference.