I can share some information about applying credits, @Kimvanlief.
Instead of a refund, some customers prefer getting a credit they can use to reduce the balance on their next invoice. With this, there are few ways to handle credits in QuickBooks.
A credit memo can be used to record an unapplied refund. This affect the sales reports, even if you don't apply them to invoices.
Here's how:
1. Tap + New button and select Credit memo or Give credit.
2. Select the client's name and enter the credit memo details including the amount and date.
3. Once done, hit Save and close.
To apply a credit memo to an invoice:
1. Go to + New and select Receive payment.
2. Fill in the customer’s name, and other important fields.
3. In the Outstanding Transactions section, select the open invoice you want to apply the credit memo to.
4. Proceed to Credits section and select the credit memo you want to apply.
5. For the open invoice in the Payment column, enter the credit amount you want to apply.
6. Make sure to leave the fields for Payment method, Reference no, Deposit to, and Amount received blank.
7. Fill out the rest of the form, including the Payment date.
8. Make sure the total to pay (if any) is correct after applying the credit memo.
9. Once you're done, hit Save and close.
You can refer to this article to learn how to turn on the credit memo auto-apply feature.
Please let me know if you need further help with correcting double payment. I'll be glad to work with you any time.
