The small Spanish town of Tarifa is sometimes credited with being the origin of the word "tariff", since it was the first port in history to charge merchants for the use of its docks. The name "Tarifa" itself is derived from the name of the Berber warrior, Tarif ibn Malik. However, other sources assume that the origin of tariff is the Italian word tariffa translated as "list of prices, book of rates", which is derived from the Arabic ta'rif meaning "making known" or "to define".
A customs duty or due is the indirect tax levied on the import or export of goods in international trade. In economic sense, a duty is also a kind of consumption tax. A duty levied on goods being imported is referred to as an import duty. Similarly, a duty levied on exports is called an export duty. A tariff, which is actually a list of commodities along with the leviable rate (amount) of customs duty, is popularly referred to as a customs duty.
In the Kingdom of England, customs duties were typically part of the customary revenue of the king, and therefore did not need parliamentary consent to be levied, unlike excise duty, land tax, or other forms of taxes. This is no longer the case.
Customs duty is calculated on the determination of the assessable value in case of those items for which the duty is levied ad valorem. This is often the transaction value unless a customs officer determines assessable value in accordance with the Harmonized System.