 While each country often in principle provides only one form of non-preferential certificate of origin (or even no form at all), the form of preferential certificate of origin differs from one trade agreement to another.It means that the more trade agreements a country participates in, the more forms of preferential certificate of origin its traders may need to be familiar with.To claim preference under a certain trade agreement, traders must use exactly the form of certificate of origin devised for that agreement.