Let me help you clear the open balance due to old invoices in QuickBooks Online (QBO), essentialglassrepair.

We appreciate you for providing a screenshot of your concern to better isolate the issue. Since there were previously invoices created on a separate platform before making the switch to QuickBooks Online (QBO), we can create a credit memo. Then, edit the check to update the account to the Account/Receivable account. Just open the check edit the Category as to Accounts Receivable and press Done.  

Once done, we can link the credit memo and check in the Receive Payment section. Here's how to create  a credit memo:

1. Click the + New Plus icon. 
2. Choose Credit memo.
3. From the Customer dropdown, select the customer's name.
4. Enter the credit memo details, such as the date and the amount. You can create a custom credit service item so you can quickly add it to credit memos as a single line item.
5. When you're done, press Save and close.

Then, link the credit memo and check in the Receive Payment section by following the steps below: 

1. Click the + New Plus icon.
2. Tap Receive payment.
3. From the Customer dropdown, choose the customer.
4. In the Outstanding Transactions section, select the open invoice you want to apply the credit memo to.
5. In the Credits section, select the credit memos you want to apply. You won't see the credits section if you have not created the credit memo.
6. For the open invoice in the Payment column, enter how much of the credit you want to apply.
7. Leave the Payment method, Reference no, Deposit to, and Amount received fields blank.
8. Fill out the rest of the form, including the Payment date.
9. Make sure the total is correct after applying the credit memo.
10. When you're done, press Save and close.

For your reference, you may check out this article about credit memos, credit, or refunds. Enter and apply credit memos and delayed credits in QuickBooks Online. Additionally, I'll also share this link where you can browse articles that can help you organize payments in QBO: Invoices and Payments Help Articles in QuickBooks Online.

You're more than welcome to drop by if you have questions about managing your invoices. Do you need to run some payroll reports for the next current period? Or would you like to take care of taxes in QuickBooks? Let me know and I'll lend a hand again.