Hi there,

Thanks for posting in the Community. 

Turning off GST in QuickBooks Online is unavailable at this time. You'll have to edit each transaction and set the tax code to Out of Scope. That way, there's no GTS calculated and reported in your BAS.

If you have an accountant that has QuickBooks Online for Accountants, you can add them as an accountant user in your QBO account, and they can help you reclassify your transactions at once to the correct GST code.

Please let me know if you have any additional questions. I'm always willing to assist.