Hi Trevor1511, 

Let me share with you some information on GST. Once you enabled the GST option in QuickBooks Online, you can no longer turn it off. However, you can set the default tax rate to out of scope on your settings.

Here's how: 

1. Go to Gear icon and select Account and Settings.
2. Select Advanced and go to Accounting section.
3. On Default tax rate selection drop-down menu, select Out of Scope. 
4. Select Save and Done. 

Also, you may check on this article for your reference: How do I turn off GST.

Feel free to drop a comment below if you have any other questions. Have a great day!