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The customs terms that decide what you pay
A plain-English glossary of import-duty and classification terms — each with a worked example and links to the codes, tools and guides that put it to use.
Classification
General Rules of Interpretation
The six legal rules, applied in order, that decide which HTS heading a product belongs to when more than one could apply.
Read definition →Harmonized Tariff Schedule
The official US list of every imported product and its duty rate, maintained by the US International Trade Commission and used by CBP to assess duty.
Read definition →HS code
The six-digit international product code maintained by the World Customs Organization, shared by every country that uses the Harmonized System.
Read definition →HTS code
The 10-digit US import code built on the six-digit HS root; the number CBP uses to assess duty on goods entering the United States.
Read definition →Schedule B
The 10-digit US export classification administered by the Census Bureau, built on the same HS root as the HTS but used for export statistics, not duty.
Read definition →Duty & fees
Ad valorem duty
A duty charged as a percentage of the customs value — the most common form of import duty (e.g. 5% of the entered value).
Read definition →Harbor Maintenance Fee (HMF)
A fee of 0.125% of the customs value on cargo arriving by ocean at a US port; it funds port and harbor maintenance and has no minimum or maximum.
Read definition →Landed cost
The true, all-in cost of getting a product to your door: product cost, freight, insurance, duty and customs fees combined.
Read definition →Merchandise Processing Fee (MPF)
A CBP fee for processing a formal entry: 0.3464% of the customs value, with a per-entry minimum and maximum that CBP adjusts each fiscal year.
Read definition →Tariff rate
The percentage or per-unit charge applied to an imported product, read from its HTS line plus any additional Chapter 99 measures for its origin.
Read definition →Tariff measures
Country of origin
Where a product was produced or substantially transformed — not where it was bought or shipped from — which decides the additional tariffs that apply.
Read definition →De minimis
The rule that let low-value shipments (historically up to $800) enter the US duty-free with minimal formalities — significantly tightened in 2025.
Read definition →Section 232
US tariffs on imports deemed a national-security risk — most notably steel and aluminum — imposed under Section 232 of the Trade Expansion Act of 1962.
Read definition →Section 301
Additional US tariffs on Chinese-origin goods, imposed under Section 301 of the Trade Act of 1974 and published by USTR across four lists.
Read definition →Put the definitions to work
Describe a product and get its HS/HTS code, the sourced duty rate and the full landed cost — with every term above applied for you.