关税(tariff)，亦称customs duty。
商品通过关境时徵收的一种税。通常被徵收关税的物件是进口货物，其中可能是指对所有的外国商品徵税或者只对在关境外生产的商品徵税。关税有可能在边境直接徵收，也可能通过要求商家提前购买进口许可权或通过限定进口商品的数量来徵收。过境税是指关境对过境商品所徵收的一种税。关税为国家财政收入和地方企业保护提供了有力支援。通过提高进口价格，可鼓励国内的生产者提高商品的价格，或者利用税收优势制定较低的商品价格，从而吸引更多的消费者。关税通常用来保护国家的「新兴产业」和状况不景气的产业。因为其影响商品价格，造成国内消费者消费升高，且该政策不利於提高国内产业的生产效率，有时关税政策也受到指责。关税价格根据各国之间的协商与签署的协定来制定。亦请参阅General Agreement on Tariffs and Trade (GATT)、trade agreement、World Trade Organization。
English version：
tariff
Tax levied on a commodity traded across international borders. Usually assessed on imports, tariffs may apply to all foreign goods or only to goods produced outside the borders of a customs union. A tariff may be assessed directly, at the border, or indirectly, by requiring the prior purchase of a license or permit to import specified quantities of the good. Transit duties or taxes may be levied on goods passing through a customs area en route to another destination. Tariffs provide a source of revenue and protect local industry. By driving up the price of the imported item, they allow domestic competitors either to charge higher prices for their goods or to take advantage of their own lighter taxes to charge lower prices and attract more customers. Tariffs are often used to protect “infant industries” or to safeguard older industries that are in decline. They are sometimes criticized for imposing hidden costs on domestic consumers and encouraging inefficiency in domestic industries. Tariffs are subject to negotiation and treaty among nations (see General Agreement on Tariffs and Trade, trade agreement, World Trade Organization).
