Sometimes, when you've refunded a customer with a refund voucher, you might need to void that voucher so that it can no longer be used.
How to void a refund voucher
Open the 'Promote' tab.
Select 'Voucher codes' from the left hand menu.
Select the 'Refund voucher codes' tab to view a list of all of your voucher codes.
Use the three-dot menu to select 'Void'.
In the pop-up window, select the button called 'Void voucher code' to cancel your refund voucher.