Invoice is being created in sap however idoc shows still error with error message "External document number<ext doc no> does not match reference document number<generated invoice number> " system is assigning newly generated invoice number to X...

Hi, i am trying to get self billing running. The customer should send an IDOC of type GSVERF with message type SBINV. A new invoice for the referenced SD document should be created from the IDOC. When posting the IDOC an error message is thrown: ...