I appreciate you joining this thread, kkbmar. Let me share information to help you write off old and partially paid invoices in your online account.

With QuickBooks, you may consider creating credit memos for the remaining unpaid balances from the invoice. The steps shared by my colleague, CharleneMaeF above, have similar processes when writing off customer invoices that were paid partially. Thus, it's best to run an Accounts Receivable Aging Detail report to help you review all bills that are considered bad debts. To do this:

1. Go to Reports and enter the Accounts Receivable Aging Detail report from the search section.
2. Check which outstanding accounts receivable should be written off.

Once reviewed, you may follow Steps 2 & 3 outlined in this article when creating a bad debt expense account and item: Write off bad debt in QuickBooks Online.

Once done, enter the remaining amount balances from an invoice when creating credit memos for the bad debt. You may refer to the steps below:

1. Go to the + New icon and select Credit memo.
2. Choose the customer from the Customer ▼ dropdown.
3. In the Product/Service section, select Bad Debts.
4. Under the Amount column, enter the remaining balance to write off.
5. In the Message displayed on statement box, enter “Bad Debt.”
6. Then, select Save and Close.

Moreover, you can run specific reports to help review your business finances and other accounting data.

I'll keep this thread available if there's anything else you need further assistance with when managing sales transactions in your account. Just let me know, so I can provide additional help. Keep safe!