In both the EU customs union and, from 1 January 2021, the UK customs union, for most goods customs duty is an ad valorum duty based upon the value of the goods. The standard customs duty rate applicable to goods is available in the relevant tariff. The UK global tariff is available via gov.uk and the EU tariff is available on the EU commission website.
The tariff classifies goods by giving them a commodity code, based on an internationally agreed system (¶77070). As well as the standard duty rate for each code, the tariff contains information on other factors relevant to the import of those particular goods.