Tax Analysts provides news, analysis, and commentary on tax-related topics, including customs duties. Customs duties are taxes levied on goods crossing international borders, and help countries control the flow of goods into their countries, especially prohibited or restricted goods. These include animals and animal parts, hazardous materials, and plants. Customs duties also allow countries to raise revenues and protect their economies from international competition. Customs duties make up a category of indirect tax.

Countries usually have a customs department administering and collecting duties on imported goods, as well as inspecting goods, determining fees, and imposing penalties owed on such items. Calculation of customs duties can be based on a fixed percentage of the value of goods (ad valorem duties), factors such as quantity or weight (specific rate duties) or a combination of ad valorem duties and another duty rate (compound duties).

Customs duties laws vary from country to country, and some products are exempt from duty or are calculated at lower duty rates depending on free trade agreements between certain countries. The Harmonized System code was created by the World Customs Organization to help with assessing customs duties. Under this system, products are assigned an identification code so that every country can set their own rates while also referring to a standard product code.

Importers can commit customs duties evasion by under-invoicing goods (understating the price of a good as being lower than the price actually paid) or misinvoicing (manipulating the price, quality, or quantity of goods). Criminals can also bypass customs duties completely through illegal smuggling.