As of Release 3.0, you have the option of storing customs tariff preference data in the vendor master record and the purchasing info record.
This allows you, for example, to mark a material as a preference material. This means that lower customs tariffs apply to this material if it is imported from a certain country or region.
The customs preference data are stored in the vendor master record and in the purchasing info record under the menu "Extras -> Customs preference".
For further information, refer to the document "MM/SD Foreign Trade: Preference Determination".