You need one whenever you intend to claim a preferential duty rate, and often for customs clearance regardless. It is a customs declaration stating that goods on a specific invoice originate in a particular country under a specific set of origin rules — not a status your supplier holds. Three consequences catch importers. It is per consignment, tied to an invoice and a tariff line. It is issued in the exporting country by that country designated authority, at or before shipment, so it cannot be retro-fitted after goods clear. And it only produces a saving if the destination has that tariff line in a liberalised category — a valid certificate against a line the importing country excluded is entirely valid and saves nothing, which is the most common disappointment in AfCFTA claims. The origin test itself is either wholly obtained, meaning goods entirely produced in one country such as raw cocoa beans or unroasted coffee, or substantially transformed, meaning goods using imported inputs that meet a product-specific rule, usually a change in tariff classification or a regional value content threshold. Different regimes use different forms and rules: an AfCFTA certificate for intra-African preference is not the same instrument as an AGOA claim into the United States. Check the destination tariff schedule before you assume a duty saving exists to be claimed.