1. A method for managing trade preferences in business systems, comprising: performing the following using a processor; receiving input from a user of a trade services system connected to at least one business system, displaying information regarding which administrative units of a business are assigned to the user of the trade services system based on the user's input and information from the at least one business system; modifying the information regarding which administrative units of the business are assigned to the user of the trade services system based on the input from the user; selecting at least one administrative unit of the business that is assigned to the user of the trade services system for preference processing based on the input from the user; displaying information regarding which legal units of the business and which trade preference rule sets of the trade services system are relevant to the selected administrative unit for preference processing; selecting at least one relevant legal unit of the business and one relevant trade preference rule set of the trade services system for preference processing based on the input from the user; and implementing a sequence of preference processing steps based on the selected legal unit of the business, the selected trade preference rule set and the input from the user.