This feature is particularly useful if you would like to delete an invoice that has been marked as "Paid" previously. Paid invoices cannot be deleted due to the discrepancies and confusion it could lead to in accounting, so now each admin has the option to mark an invoice as unpaid in order to change the payment method, or delete the order.
Check that you are using the new version of our invoicing tool in Settings > Admin > Invoices > Invoice Tool Version
If the Invoice Tool Version is 'New', then you have the ability to change the payment status of an invoice that you had previously created and marked as paid, to unpaid.
To do this, just go to Settings > Admin > Admin Tools > Undo Invoice Payment.
Each invoice has its own unique ID and you will need to input the invoice ID to update it as unpaid.
Please note that when we mention invoice we are referring to what is otherwise known as a statement. By invoice we do not mean just one order. An invoice/statement would be used to group various orders to report them and collect payment for them collectively from customers/business accounts, or to be sent to an accounting integration.
Please also bear in mind that using this feature does not initiate a refund automatically.