Hello, @LaurensPP.

When you create a credit memo, you have the option to apply it to an invoice or give a refund. Let me guide you on how it works.

Here's how to create credit memo:

1. Click the Customers menu.
2. Choose to Create Credit Memo.
3. Select the name of the Customer: Job.
4. Enter the credit memo details.
5. Click Save and Close.

Once the credit memo is created, you can now write a check with the total amount of the refund.

Lastly, to avoid getting open credit memos and unapplied refund checks, let's link the credit memo to the check.  

You can refer to this article for more detailed steps: Give your customer credit or refund in QuickBooks Desktop for Windows.

Fill me in if you have other questions. I'm always here to help.