If you've incorrectly allocated a supplier credit note to a supplier invoice, you can unallocate them.  

Unallocate a PC from a PI

1. Go to Suppliers, select the required supplier, then select Activity.
2. Select the PC transaction to unallocate, select Unallocate transaction, then press Yes.
   TIP:

   If you can't press 'Unallocate transaction', follow our Why can't I unallocate a transaction? article.