Thanks for getting back to us, @lena21.
In QuickBooks Online (QBO), there are only two ways on how to process a refund to a customer which was already shared by my colleague above. Since your customer is not using a credit card, I suggest looking for a third-party application as a workaround.
This can be done by going to the Apps tab in the left panel, and enter a keyword in the search field. You can also click this link provided above for any apps you can find that’s integrated with QuickBooks: https://apps.intuit.com/app/apps/home.
Just in case, I'll add this article for future reference: Record a customer refund in QuickBooks Online.
Reach out to me in the comment section below if you have any other questions or concerns, and I'll get back to you as soon as possible. I'm always here to help. Have a great day!
