Tariff
A tariff is a duty — a tax — levied on goods crossing a border. Ad valorem tariffs are a percentage of the customs value; specific tariffs are a fixed amount per unit or weight; compound tariffs combine both. The applicable rate is found by the product's HS code in the national tariff schedule.
Tariffs are the direct cost of importing, and the reason HS classification and country of origin matter so much — together they set the duty rate, which flows straight into a product's landed cost and competitiveness.
The tariff is the price of crossing the border. It is why an HS code and a certificate of origin are worth getting right — a few percentage points of duty on every shipment compounds into a serious number, and preferential origin can cut it to zero.
A shipment with a customs (CIF) value of $50,000 under a 5% ad valorem tariff owes $50,000 × 5% = $2,500 in duty — before any VAT or other import taxes.
What is the difference between an ad valorem and a specific tariff?
An ad valorem tariff is a percentage of the goods' value; a specific tariff is a fixed charge per unit or per kilogram, regardless of value.
What value is duty calculated on?
Usually the customs value, which in most regimes is the CIF value — cost of the goods plus insurance and freight to the border.