A tariff is charged to the importer of record when goods enter a country. Who ultimately bears that cost is a separate question, decided by market structure rather than by the customs form.
The payment point is not the resting point
Customs collects duty from the importing business, calculated on a declared value and a classification code for the goods.
That business then decides whether to absorb the cost, pass it forward to its customers, or push it back to the supplier through renegotiated prices.
The outcome depends on who has alternatives. A buyer with other sources pushes the cost back; a supplier with other buyers refuses, and the importer is left holding it.
Contracts delay the effect
Supply agreements are usually fixed for a period, so a tariff introduced today meets prices agreed months ago.
Shipments already at sea are also priced under the old terms, which is why the retail effect of a tariff appears well after the announcement.
When those contracts come up for renewal, the accumulated cost is renegotiated in one step, and the price change that follows looks larger and more abrupt than the tariff itself.
Classification is where the money is
Duty rates depend on the tariff code assigned to a product, and codes are narrow, technical and frequently disputed.
A small change in specification can shift an item between codes with different rates, so design decisions are sometimes made with the tariff schedule in view.
Customs authorities audit classification precisely because of this, and a reclassification applied retrospectively can produce a bill covering years of imports.
Intermediate goods multiply the effect
Tariffs on components land on domestic manufacturers rather than on foreign competitors, since it is the domestic factory that imports the part.
A component crossing a border several times during assembly can attract duty at each crossing, compounding the effect on the finished product.
This is why manufacturers often oppose tariffs on inputs in industries where the finished goods are protected by tariffs of their own.
Supply chains reroute rather than absorb
Given time, buyers shift sourcing to countries outside the measure, and the trade flow moves rather than shrinking.
Some of that movement is genuine relocation of production, and some is minimal processing in a third country intended to change the declared origin.
Rules of origin exist to separate the two, and enforcing them is what determines whether a tariff changes production patterns or merely changes paperwork.