When businesses declare goods for import, they must state the customs value of the goods in the customs declaration. The customs value is also needed to calculate customs duties. Determining the customs value can be challenging. For this reason, the WTO’s agreement on customs valuation, which is applicable to all WTO member states, defines rules for a fair, uniform, and neutral valuation of imported goods. For example, it sets out that the primary basis to determining the customs value is to be “the transaction value, that is the price actually paid or payable for the goods when sold for export to the country of importation“ (Article 1). Further criteria must be taken into account. This agreement will continue to apply to goods imported into the UK after January 1, 2021.