Hello, SueTy.

Thanks for replying to us. Since the refund didn't go through, you can void the check. This way, the check will remove as an expense. Then you can add a note for what this void check is for. 

Once done voiding the check, you'll have to manually process the refund and enter them into QuickBooks Online. You can click this article to see the detailed steps on how to perform the process: Void or refund customer payments in QuickBooks Online.

If you're unsure, reach out to your accountant. This can get tricky and they know how to handle the next steps. Don't have an accountant? We can help you find one. 

I'm always here if you need more help in refund your transaction. Just let me know by leaving a reply below. Keep safe and have a wonderful day!