A duty is a tax imposed by a national government on goods imported into its customs territory. In the United States, duties are collected by CBP at the time of entry and are the primary mechanism by which the government regulates the price competitiveness of foreign goods. Duty law is codified in Title 19 of the U.S. Code and the Harmonized Tariff Schedule.
Duty is calculated using one of three mechanisms:
- Ad valorem — a percentage of the customs value (e.g., 6.5%)
- Specific — a fixed amount per unit of weight, volume, or count (e.g., $0.077/kg)
- Compound — a combination of both (e.g., 5% + $0.10/kg)
Most U.S. tariff lines are ad valorem. Specific and compound duties survive primarily in agricultural products, textiles, and a few raw-material categories.
Duty is owed by the importer of record and secured by an entry bond. The duty amount on an entry is estimated at the time of entry, then finalized at liquidation (typically 314 days after entry). After liquidation, the only remedy for an overpayment is a protest filed within 180 days.
In modern U.S. practice, "duty" usually refers to the base Column 1 rate. Several other charges look and behave like duty but are technically separate:
- Section 301 tariffs (USTR action against unfair trade practices)
- Section 232 tariffs (national security)
- Section 122 balance-of-payments tariffs
- Antidumping and countervailing duties
- IEEPA-based tariffs (fentanyl, reciprocal, etc.)
These trade remedies stack on top of base duty and apply through Chapter 99 of the HTS.
Duty is distinct from user fees like MPF and HMF, which fund CBP operations and harbor maintenance rather than serving as protective trade measures.