Use creditors invoice number instead of generic Bill number as primary reference.

 It would make more sense to have the creditors invoice number as the primary reference instead of a generic bill number. it's easy at a glance to reconcile statements and choose the correct invoice when making payments when looking at the same information. The Bill number should just be an internal reference and isn't helpful in real terms. This would also help with the issue others have with inadvertent duplication of invoice entry.