Trade compliance · United States

How U.S. import duty is calculated, explained

The number an importer actually owes is rarely just the tariff rate. A U.S. import charge is built up in layers — a base duty set by the goods' classification, then policy surcharges, then user fees, with case-by-case antidumping duties on top. This is a plain-language map of how those layers stack, and where to check the current numbers for a specific code.

Rates, fee minimums and the covered-product lists change often and are set by several agencies, so this page does not reproduce specific current figures. To compute the duty for an exact HTS code, country of origin and shipment value, use the live calculator linked below — it derives the numbers from the maintained USITC HTS data.

The layers of a U.S. import charge

1. 01

   Base duty — the HTS classification

   Every imported good is classified under a 10-digit code in the Harmonized Tariff Schedule of the United States (HTSUS), published by the U.S. International Trade Commission. The code determines the base, or “general”, duty rate — which can be zero, a percentage of the value (ad valorem), a per-unit amount (specific), or a mix. Getting the classification right is the whole game: it sets the base rate and decides which of the surcharges below even apply.

2. 02

   Trade-remedy surcharges — Section 301, 232, 122

   On top of the base rate, additional duties may apply because of trade-policy actions. Section 301 (Trade Act of 1974) covers additional duties on specified goods of certain countries; Section 232 (Trade Expansion Act of 1962) covers national-security measures such as those on steel, aluminum and derivatives; Section 122 is a temporary balance-of-payments surcharge. Whether any apply depends on the HTS code and the country of origin — and the covered lists are amended frequently.

3. 03

   User fees — MPF and HMF

   Most formal entries also carry user fees collected by U.S. Customs and Border Protection: the Merchandise Processing Fee (MPF), an ad valorem fee with a published minimum and maximum that CBP adjusts, and the Harbor Maintenance Fee (HMF) on goods arriving by ocean. These are charged on the customs value regardless of the duty rate, so even a duty-free good can owe them.

4. 04

   Antidumping & countervailing duties (AD/CVD)

   Separately, specific goods from specific countries can be subject to antidumping or countervailing duties under orders administered by the U.S. Department of Commerce and the ITC. These are case-by-case, can be large, and are easy to miss — if an AD/CVD order covers your product and origin, it applies on top of everything above.

Putting it together — the customs value

The percentages above are applied to the customs value of the goods (most often the transaction value — broadly, the price paid or payable, with statutory additions). Base duty, Section 301/232/122 surcharges and AD/CVD each apply to that value per their own rules, the user fees apply on top, and the sum is the duty and fees owed at entry — before brokerage, freight and other landed-cost components. The single most important input is the HTS classification, because it decides both the base rate and which surcharges are in scope.

Where to verify (authoritative sources)

These are the official sources. Always confirm the current rates, fee amounts and covered codes against them before relying on anything — including this page.

• USITC — Harmonized Tariff Schedule (HTSUS) The official classification and base duty rates, searchable by code or description.
• USTR — Section 301 tariff actions The investigations, covered-product lists and additional-duty actions.
• U.S. Dept. of Commerce / BIS — Section 232 National-security tariff and quota measures (steel, aluminum and derivatives).
• U.S. Customs and Border Protection (CBP) Entry, user fees (MPF/HMF), rulings and the current fee minimums/maximums.

Related: The Merchandise Processing Fee (MPF), explained — the user fee in this stack · Section 301 vs 232 vs AD/CVD — the extra duties that layer on · De minimis (Section 321) — why low-value parcels now compute this duty too · Canada's surtax on U.S. goods — the mirror-image measures on the Canadian side.

This is an independent, plain-language explainer produced by an autonomously operated software workshop under human oversight. It is not legal, customs or tax advice, is not the official version of any tariff schedule, statute or agency notice, and may be out of date. Always verify against the USITC, USTR, Commerce/BIS and CBP sources above. No affiliation with, or endorsement by, any U.S. government agency is implied.