I can help you refund your customer and print it out, @rock and roll.

Use a refund receipt to record a refund to a customer to print them right after. 

Here's how:

1. Go to the + New and select Refund receipt.
2. Select the customer you want to refund from the Customer dropdown.
3. Enter the details in the fields using the same info from the original sale. To credit back their credit card, in Payment method, select Credit card. To credit back their bank account, in Payment method, select Bank.
4. In Refund from, select which payment method and account you wish to refund the customer from.
5. Click on Save and close once you're done. 

Check these articles for more information:

• Record a customer refund in QuickBooks Online
• Void or refund customer payments in QuickBooks Online

Here are some articles you can read for ideas about how you can work with your sales in QuickBooks: Sales and Customers for QuickBooks Online.

I'm always here if you have questions in recording your transactions. Keep safe and have a wonderful day!