Having trouble invoicing with tax on the phone app, desktop version works fine. Help.

Hello, nathalieu2. 

I'll share some steps that can help us make sure that your mobile app is recording the invoice with tax properly. We can reset the application to refresh it. Follow the steps below:    

If you're using an Android device:

1. Go to the More Options ⋮ menu. 
2. Select Settings.   
3. Tap Refresh Data, and then choose Yes. 

For iOS:

1. Go to Help & Feedback at the top menu bar.  
2. Choose Reset App Data. Then Refresh.     

For more detailed steps of the process, check out this article: Troubleshooting Quick-Start Guide for the QuickBooks app.      

Then close and reopen the app to check if that works. If still get the same result, let's uninstall and reinstall the app to start on a clean cliche.      

For additional reference, I've attached an article about the mobile app features: Compare mobile app features. 

If there’s anything else I can help you with, click the Reply button and post a comment. I’ll get back to assist further. Have a great rest of the day.