The following information is needed to implement a new EDI message in an SAP environment if you are implementing internally using your own EDI translator system and team. It is a lot of information for one message, but it is necessary in order to understand exactly what data needs to be consumed or produced by your applications and business processes.
Every electronic message will require this information. If you have 1,000 trading partners each sending an electronic invoice, then you would need 1,000 implementation documents containing the information listed below. Why 1,000 documents, because each will be tested separately and often will contain small differences in the data sent in the files, plus the trading partner contact information will be different each time.
Read the full article here: SAP e-Invoicing Compliance: EDI Message Implementation Information for SAP Users