A Preferential Certificate of Origin (PCO) certifies the originating status of a good under a specific Free Trade Agreement (FTA) and allows the good to be imported into the importing country at a reduced or zero tariff rate. An Ordinary Certificate of Origin (OCO), on the other hand, is a unilateral document that certifies the good to be of a specific origin. It does not entitle the good to any preferential tariff treatment. The good in a single export should only be covered by one CO at any one time.