When creating / editing a Purchase Invoice or Sales Invoice on the drop down for the purchase code / sales code, you can see ALL of the Purchase Codes and Sales Codes (whether you are trying to create a purchase or an invoice).
This is confusing as it can be hard to work out which is the right one if you have a purchase and sales code with similar (or the same) name.
If you are creating a Purchase Invoice, then surely you should only see the purchase codes in the drop-down. If you really want to include sales codes too, then at least have the sense to show them greyed out!
Equally when creating a Sales invoice, you should only see the sales codes in the drop-down.