SAP Message 60818 - Service charge key & not valid per &

Diagnosis
You have entered a service charge key which is not defined for therental unit or not valid for the date entered.

System Response
Your entry is not accepted.

Procedure
Correct the service charge key, enter a date for which the servicecharge key is valid or, if a settlement unit has not yet been defined,create a new settlement unit concerning the service charge key and therental unit of the agreement, in the settlement unit dialog.