I still am unable to charge sales tax to taxable customers. Or create sun customers. Mobile platform. Everything has to be double worked on the computer.

Thanks for coming back, @melvin1. I appreciate you for giving us updates about the troubleshooting steps we initially performed for the mobile app to charge sales taxes to your invoices in QuickBooks Online. Allow me to further assist you and ensure that this will be sorted out in no time.

Since the issue persists after making sure that your customers are liable to pay sales taxes, refreshing, uninstalling, and reinstalling the app, I'd recommend getting in touch with our Technical Support Team given that they have all the tools required to safely look at your account through screen sharing in order to more precisely pinpoint the sales tax and invoice editing difficulty you're experiencing.

Here's how:

1. Go to the Help icon and select Contact us in the Search tab.
2. From the What can we help you with field, enter your question.
3. Click on Continue.
4. Choose either Appointment, Callback, or Chat.

When everything's good, you can utilize these articles that I've included to help you edit and add a new sales tax rate using the QuickBooks Online app: 

• Add or edit a sales tax rate in the QuickBooks Online app (iOS only)
• Add a new tax rate for a transaction using the QuickBooks Online app (Android only)

I'm still willing to help you some more if you need extra help managing your sales taxes and invoices in QuickBooks Online. Just leave a comment below and I would be glad to be of assistance. Take care.