A system for processing electronic documents includes an existing business system (or systems) connected to a separate control system. The resulting composite system provides a framework that enables a flexible and customizable process definition for handling incoming documents. Within the process definition all the processing steps which are desired for handling an incoming electronic document can be predefined. Processing steps like checking the signature and authorizing an incoming legal document can be implemented in the control system and steps like posting a goods receipt or an invoice are implemented in one of the connected business systems. The content of the incoming document is evaluated to determine which business process may be used to carry out the necessary processing steps for the incoming electronic document. The assigned business process and a related process flow sequence define the processing steps to be implemented.