(customs) A tax levied by a government on the import, export or consumption of goods. Usually a tax imposed on imports by the customs authority of a country. Duties are generally based on the value of the goods (ad valorem duties), some other factors such as weight or quantity (specific duties), or a combination of value and other factors (compound duties). See ad valorem; specific rate of duty; compound rate of duty.
(U.S. Customs) All goods imported into the United States are subject to duty or duty-free entry in accordance with their classification under the applicable items in the Harmonized Tariff Schedule of the United States (HTS or HTSUS). An annotated, loose-leaf edition of the HTS may be purchased from the Superintendent of Documents; U.S. Government Printing Office; 732 N. Capitol Street, NW; Washington, DC 20401; Tel:  (202) 512-1800; Web: www.gpo.gov/.
Note that duty rates are subject to the classification of goods by Customs. Articles that appear to be similar may have significantly different rates of duty. See classification. Note also that the actual duty paid is also determined by how Customs values the merchandise. See Harmonized Tariff Schedule; valuation.