You can cancel orders up to one week after the event.
Find and click the order, on the orders overview page.
Click Cancel Order.
A credit invoice is created, and sent to your customer.
In case the order is paid online, the funds are automatically refunded.
The attendees are removed from the list.
You can cancel an online Paid order up to one week after the event.
PayPal paid orders can be canceled up to 60 days after the Payment, due to PayPal's refund restrictions policy.
Invoice Payments don't have a time restriction.
You can only refund the full amount, it is not possible to refund an order partially for any payment method.