I cannot get the gst to add on to an invoice on an iPhone. It works with a desktop but I’m mobile and do invoices on the go.

Hello @glasstec.autogla,

Let's perform a few troubleshooting steps so you can invoice your customer with the correct taxes calculated from your mobile device.

First off, let's start by removing the cache stored on your app and mobile device. Let me show you how.

On the app:

1. Select the Menu icon at the top right.
2. Select Help & Feedback.
3. Click Refresh Data and Refresh.

On your mobile device:

1. Go to Settings.
2. Select Setting General iPhone Storage.
3. On the list of apps, select QuickBooks.
4. Click Offload App.

In the same manner, here's an article you can read to learn more about the troubleshooting steps: Troubleshooting Quick-Start Guide for the QuickBooks Online app.

On top of that, I've also included this reference for a compilation of articles you can use while working with us: GST and BAS for QuickBooks Online.

If you have any other questions, please let me know by leaving any comments below. I'll be here to lend a hand.

Do I need to do this on the app and mobile or just the mobile?

Thanks for getting back to us, glasstec.autogla. I'm here to help share a few things and clarify the suggestions shared by my colleague before following them.

The first set of steps to follow is the troubleshooting inside the app installed on your mobile device. Once done, let's try creating an invoice to check if it's now calculating your sales tax correctly.
 

But if it doesn't work, let's continue by following the second set of steps to completely fix the issue about why you're unable to create invoices with the corresponding GST. 
 

I have here invoices-related articles for your future reference and guide:

• How to edit an invoice.
• Record invoice payments in QuickBooks Online.

That's it! If you have any additional questions about GST and managing your invoices, please add them in a comment below. We're here to help.