I have an idea on what the error message is all about and help you resolve it.
It looks like you're trying to record the partial payment in the Bank deposit screen or in the Banking page. You'll encounter this error message when you select the Accounts Receivable account and assigning a tax code to it. This messes up the accounting, and the system prevents you from doing this. We can only assign a code to expense or income accounts.
You'll want to use an income account instead of Accounts Receivable when recording the partial payment. Check with your accountant to see which income account is applicable for tracking your payments. They'll ensure your books are accurate and correct when recording your transactions.
You can also use the Receive payments function instead of Bank deposit. If you haven't already done so, create an invoice first (with the correct tax code). Then, record the partial payment:
More details can be found here: Record invoice payments in QuickBooks Online.
Want to see how much you've earned from your clients? There are a variety of reports you can pull up in QuickBooks Online. For example, you can use the Profit and Loss report. Look for an article here. Our help contents have guides and steps on how you can customize and handle your data in reports.
I'm ready to help you again if you have concerns recording your transactions or with QuickBooks Online. Looking forward to you reply in this thread.