1. From the Purchases, select Purchase Invoices.
2. Open the relevant paid Purchase Invoice.
3. Select the 1 payment hyperlink under the Amount Paid. If you made multiple payments, the number will be different.
4. Select the pencil icon in the Refund column.
5. From the Amend Supplier Payment window, select Refund payment.
6. Select the Refund date and the relevant Paid from bank account.
   
7. Select Save.

The invoice now shows as outstanding and the refund shows in your bank activity as a Supplier Refund.