Today, all Customs administrations of the WTO Members value imported goods in terms of the provisions of the WTO Agreement on Customs Valuation (ACV), which was adopted in 1994. The ACV establishes a Customs valuation system that primarily bases the Customs value on the transaction value of imported goods, which is the price actually paid or payable for the goods when sold for export to the country of importation, plus certain adjustments of costs and charges.
Non-WTO Members are not obliged to apply the provisions of the ACV. A few rare countries still apply the provisions of the Convention on the Valuation of Goods of 1953 also known as the Brussels Definition of Value (BDV) for customs purposes.
The ACV is published in the WCO Compendium on Customs Valuation and is also available via the following link: https://www.wto.org/english/docs_e/legal_e/legal_e.htm#artvii
The legal basis is the Agreement on Customs Valuation (ACV) or simply the Agreement. Domesticated in Section 122 of the East African Community Customs Management Act 2004 and the Fourth Schedule to the Act.