When a system upgrade is done from an older version to 4.7, Billing
Accounting Document does not have the assignment field populated with the Invoice Number. To fix this issue a small piece of
configuration is to be done, which is as follows:
T.Code OB16 -Change View " Rules for Allocation Number "
Sort Key 000
- Allocation Number
CHANGE/DELETE THE DESCRIPTION & Save the changes
Once Agian input the Description as it was
prior to the earlier change & Save
What happened here is the system created an internal Code to get the Assignment
Field populated with the Invoice Number.