Deleting Drafts (Sales A/R and Purchasing A/P) 
You can delete A/R and A/P documents that were saved as drafts.
Procedure
From the SAP Business One Main Menu, choose
Sales – A/R 
Sales Reports Document Draft Reports 
or Purchasing
– A/P Purchasing Reports Document Draft Reports .Specify the required parameters to display the drafts you want to delete.
Select the required draft and choose
Data Remove .
NoteYou can delete only one draft at a time.
End of the note.