- This article is about import/export tariffs. For other uses, see custom.
A customs duty is a tariff or tax on the import of or export of goods. In England, customs duties were traditionally part of the customary revenue of the king, and therefore did not need parliamentary consent to be levied, unlike excise duties, land tax, or other impositions.
Customs is an authority or agency in a country responsible for collecting customs duties and for controlling the flow of people, animals and goods (including personal effects and hazardous items) in and out of the country. Depending on local legislation and regulations, the import or export of some goods may be restricted or forbidden, and the customs agency enforces these rules. The customs agency may be different from the immigration authority, which monitors persons who leave or enter the country, checking for appropriate documentation, apprehending people wanted by international search warrants, and impeding the entry of others deemed dangerous to the country.