Hi AZFB!

Thanks for joining this thread. Allow me to assist you in handling the customer overpayment.

Upon recording a customer payment with an amount more than the amount due, the Overpayment section will appear where you can select to leave the overpayment as credit. You'll want to open the payment transaction you created and check it. Please refer to this screenshot:

In addition, here's another way to create a credit memo:

1. Go to the Customers menu and select Create Credit Memos/Refunds.
2. Select your customer from the Customer:Job drop-down.
3. Enter the items you're giving credit for, then select Save & Close.
4. On the Available Credit pop-up, select Retain as an available credit. Then, OK.

I'm adding this article for your reference: Give your customer a credit or refund in QuickBooks Desktop for Windows. This explains more on how to create a credit memo or refund check.

Do you need help in balancing your books? Check this link: Reconcile an account in QuickBooks Desktop. This also explains how to match your bank and credit card statement to your real-life accounts.

Leave a comment again here if you have other concerns. I'll help you!