You have made the necessary settings in Customizing for the service charge settlement. Also note the accounting settings for the service charge settlement and external settlement. Read the Customizing documentation under:
To create a data exchange settlement unit (data exchange SU), choose:
Every settlement unit can be used in the external settlement. Set the
Data Exchange
indicator when you create the settlement unit. This changes the SU to a data exchange SU, which remains so for further processing.
The
Settlement Company
tab page becomes active, where you then enter special data for external settlements.
By specifying the business entity number (BE), you ensure that the data exchange SU is assigned to one BE only. If you do not enter a BE number when you create the master data, the data exchange SU can be used in all BEs.
Now follow the procedure as described in Editing Settlement Units .