A preference certificate is required for international shipping if a preferential agreement has been concluded with the country. This proof is considered as a customs document with which a lower customs tariff is used for the declared goods. As there are no customs duties within the European Customs Union, there is no need to provide proof of preferential delivery. However, there are countries outside the Union with which such a preferential agreement has been concluded. These goods have a right of preference and are in the customs procedure preferred, there are little or no customs fees. For the import and export of each country must be paid separately to the respective preference rate.