The duty payable on an imported product depends on the code it is classified under rather than on what the product is called commercially. Classification is where most import cost disputes originate.
An international system provides the framework
Goods are described using a harmonised nomenclature maintained internationally, with the leading digits standardised across participating countries.
Countries then extend the code with additional digits for their own tariff and statistical purposes, so the full code is longer than the shared portion.
This means the broad category is consistent worldwide while the applicable rate is national, which is why the same product attracts different duty in different markets.
Classification follows rules, not intuition
Interpretive rules govern how a code is selected, including the principle that a more specific description takes precedence over a general one.
Composite goods are classified by the component giving them their essential character, which is frequently the point of disagreement.
Where two headings apply equally, the rules direct the classifier to the one appearing last in numerical order, a tiebreaker that decides many marginal cases.
Small design differences move the code
A garment's fibre composition, a device's primary function, or whether an item is presented as a set can each shift the classification.
Because rates differ substantially between codes, these details have direct cost consequences that manufacturers factor into product design.
Customs authorities are aware of this, and deliberate alteration to obtain a lower rate is treated differently from a genuine design choice that happens to have that effect.
Origin is a separate determination
The applicable rate depends both on classification and on where the goods originate, since preferential agreements reduce duty for qualifying origins.
Origin is established by rules specifying how much processing must occur in a country for goods to count as originating there.
Goods assembled from components sourced widely therefore require documentation tracing the inputs, and that documentation is what supports any preferential claim.
Advance rulings reduce uncertainty
Most customs administrations allow an importer to request a binding decision on classification before goods are shipped.
A ruling protects against reassessment provided the goods match the description given, which makes accurate description the importer's responsibility.
Rules, rates and procedures vary considerably by jurisdiction and are revised regularly, so a specific import decision is a matter for a customs professional familiar with the current schedule.