Great job in performing the steps in writing off bad debt, @yunxiguo1987.

Let me share additional insights about writing off bad debt in QuickBooks Desktop.

When you offset a bad sale in the system, the figures will show up on the invoice. The write-off amount will appear as it indicates the data on what happened to the invoice that you made.

That said, the information that's showing up on your end is correct. The AR report will have a zero balance for your customer. If you happen to see any balance, you may consider reviewing the steps that you made.

Please see this article for complete details about the process: Learn what to do if you can’t collect money from a customer and need to write it off as bad debt in ...

I'm also sharing this great link that you can refer to, if you need help with writing off customer and vendor balances in QuickBooks Desktop: Two ways to remove balances.

It'd be my pleasure to help you if you have any other questions with QuickBooks. Have a good one!