There are two types of duty chargeable within the Bailiwick of Guernsey. These are Excise Duty and Import Duty (also referred to as Customs Duty).
Import or Customs Duty could be liable on any goods imported from outside the customs territory of the UK(inc NI), Jersey and Isle of Man. The rate of duty is set by the United Kingdom, and is calculated on the value of the goods and the freight charged from the originating country to the first port of call within the customs territory.
To establish how much import duty is payable on an item, use the UK Global Tariff, which can be found at www.gov.uk/trade-tariff
To work out how much duty is payable on goods imported from the USA for example:
Value of the goods + shipping cost from USA to UK (first port of call in customs territory) x duty rate = duty to be charged
To work out how much duty is payable on goods imported from France to Guernsey:
Excise duty is applied to alcohol, tobacco and some fuels imported into or manufactured in the Bailiwick. Excise duty is set by the States of Guernsey in accordance with local government requirements. The rates are reviewed annually by the States of Guernsey and set at budget time, which is usually in October. They cover Guernsey and Alderney; Sark sets its' own rates via the Chief Pleas.