Entering a refund for your customer is so easy, truk4u.

You'll want to enter a refund for your credit card or an ACH payment for a sales receipt. Please follow the steps below on how to do this: 

1. Click + New.
2. Select Refund receipt.
3. Select the customer you want to refund from the Customer ▼ dropdown.
4. Fill out the fields using the same info from the original sale. To credit back their credit card, in Payment Method, choose QuickBooks Credit - Credit card. To credit back their bank account, in Payment Method, choose QuickBooks Credit - Bank.
5. In Refund From, choose which payment method and account you wish to refund the customer from.
6. Click Save and close.

To refund an invoice that the customer already paid:

1. Click + New.
2. Select Refund receipt.
3. Select the customer you want to refund from the Customer ▼ dropdown.
4. Fill out the fields using the info from the original sale.
5. Choose which payment method and account you wish to refund the customer from. Note: You can't refund an ACH payment to the customer’s bank account. You'll need to choose another refund method (cash, check, or store credit).
6. Click Save and close.

For reference, you can run and customize reports in QuickBooks Online to show the information you need.

Drop a comment on this thread if you have other questions about refunds. I'm here to assist you further for any other queries.