Diagnosis
You can only use this billing type to create billing documents withreference to another billing document. However, you did not specify areference billing document.

Procedure for System Administration
This billing type &V2& is assigned to a document class &V1& that copiesthe official document number
from another billing document to this one.
Check the Customizing settings for official document numbering in theIMG activity Define Document Classes andAssign Billing Types to Document Classes.