Diagnosis
You have changed the assignment of the settlement variants to thesettlement unit or the validity period in such a way that the resultingsettlement periods are inconsistent with the cost collectors alreadygenerated.

System Response
The system does not allow such a change.

Procedure
Change the settlement variant back to the original assignment.
If you have changed the validity period of a settlement unit such thatthe end date of the settlement unit is before a generated and postedcost collector, that cost collector may not be deleted.