I'll help you in resolving that, cglover123.

As mentioned above, the negative balance in your Accounts Receivable Aging Summary/Detail report represents the customer overpayments retained as available credits. To get rid of them, you can use the credit toward an invoice or refund the customer.

Feel free to follow these steps in giving a refund:

1. Go to the Banking menu, then choose Write Checks.
2. Choose the appropriate bank account.
3. Enter the appropriate check number and date.
4. In the Pay To The Order Of field, enter the customer that overpaid you.
5. Fill in the amount of the overpayment (credit balance) you wish to refund.
6. From the Expenses tab, click the Account drop-down menu and then choose Accounts Receivable.
7. Enter the same customer in the Customer:Job column.
8. Click Save & Close.

Once done, you'll have to apply the check refund to the overpayment credit so these two items won't appear as open: 

1. Go to the Customers menu.
2. Choose Receive Payments.
3. From the Received from drop-down menu, select the appropriate customer.
4. Click the Discounts and Credits icon.
5. From the Available Credits section, select the check you created and then hit Done.
6. If you see a prompt to confirm the transfer, just choose Yes.
7. Click Save & Close to complete the process.

If you want to apply the credit to an invoice, here's how to do it:

1. Go to the Customers menu.
2. Choose Receive Payments.
3. From the Received from drop-down menu, select the appropriate customer.
4. Tick the checkbox of the pending invoice, then click the Discounts and Credits icon.
5. From the Available Credits section, select the customer overpayment.
6. Click Done, then hit Save & Close.

Another thing that you can do is entering the overpayment as a tip. You may refer to this article to learn more about the process: Record an invoice overpayment as a tip. Take note that this is intended for QuickBooks Online. Although, you can use the same procedures for QuickBooks Desktop.

I also recommend checking our A/R Workflow Guide to learn the different ways of tracking customer transactions in QuickBooks Desktop.

Stay in touch with me if you need additional assistance in completing your other tasks. Have a safe and productive week ahead.