You can refund or cancel a card transaction from within your Circle Account. Navigate to Merchant Payments from the sidebar menu and select Payments.
Select the transaction you would like to either refund or cancel. Once you select the transaction, you will be directed to a screen with a more detailed view. You will see a kebab menu in the upper right-hand corner, denoted by three little dots. Click this, and you will be presented with the option to either cancel or refund a transaction, depending on the status.