I can help you handle billable expenses in QuickBooks Online (QBO), @cpakc.

The billable expenses feature is only available for QBO Plus and Advanced. Thus, you're unable to see that option on your client's QBO Essentials account.

For more insights, please check out this article: Delete customer with unbilled charges.

Also, it looks like you've imported your data from QuickBooks Desktop with billable expenses charges. If so, you don't have an option to get rid of them by yourself manually. Thus, getting in touch with our support team is the best option at this point.

One of our representatives can help remove those billable expenses linked with some customers for you. Before you proceed, I suggest checking our support hours to make sure they can assist you timely.

Here's how to contact our support:

1. Click the Help (?) menu at the top, and then type Contact Us.
2. Choose Talk to a human, and then select I still need a human.
3. Choose the Never mind option, and then click Contact Us again.
   
4. Enter your question or concern on the search box like "I want to remove all billable expenses for inactive customers."
5. Click Let's Talk.
   
6. Pick either Get a call or Start messaging option.
   
7. Follow the on-screen prompts to proceed.

For your other concern, you can make the invoice total equal zero by creating a line item with a negative value that's equal to the outstanding amount (see screenshot).

Then, make sure to click Save and close instead of Save and send when saving your invoices. Also, please ensure to turn off the auto-reminder feature. This way, QuickBooks won't send them to your customers automatically.

Lastly, you can customize your invoices to personalize the details you want.

Stay in touch with me if you need a hand with managing your invoices in QuickBooks. I'm always around to assist you.