Diagnosis
According to your Customizing for document class &V2& and country &V3&,the official document number needs to be transferred to the R/3 back-endsystem.
However, the billing document &V1& has not been transferred to theback-end system. If you canceled the billing document now, the officialdocument number would not be transferred to the back-end system.

Procedure
Transfer the billing document &V1& to the R/3 back-end system beforecanceling it.