When selling tickets for an event, you may be in situations where you will have to cancel or refund orders for specific customers. Shopify has a help page on this topic as well.
All order refunds are managed through Shopify; you can search a customer's name or order information on the orders page to find their order. Once on the order page, you'll see an action at the top of the page called "Refund" tap this to begin the refund process:
You can choose which line items to refund and return, then hit the Refund button at the bottom to complete the refund.
How will a refund affect event tickets purchased with the order
If an order with tickets is refunded, Evey will not take any action to cancel the tickets automatically. However, you can change this under Settings -> Order Settings so that when an order is refunded, all tickets are marked as canceled in the app. Learn more about handling refunds and canceling tickets.