QB Issue Resolution:

Once GST is turned on it cannot be turned off, however if you recently set your QuickBooks Online file you can reset your file and start again (provided it us under 90 days old).

If your file is older than 90 days or you do not wish to reset your file you can change your default tax rate to Out of Scope and your transactions will be be posted to GST.  For assistance on changing your default tax rate, see How to I set up a default tax rate for transactions (Inclusive / Exclusive of GST)? 

Resolution for Issue 'is it possible to turn off gst in QB?' available: Yes (Solved).
Source: Intuit Community forum.

is it possible to turn off gst in QB?: this issue or error code is a known issue in Quickbooks Online (QBO) and/or Quickbooks. Support for this issue is available either by self-service or paid support options. Experts are available to resolve your Quickbooks issue to ensure minimal downtime and continue running your business. First try to resolve the issue yourself by looking for a resolution described below. If it is a complex issue or you are unable to solve the issue, you may contact us by clicking here or by using other support options.

Support for Default tax rate
Quickbooks Repair Pro will resolve it efficiently and affordably. Guaranteed resolution of your issue, or you pay nothing!

Error Recovery for Default tax rate [Canada]
E-Tech is the #1 Quickbooks data migration and Conversion service provider.

Get 50% off Quickbooks Online

Click Here for 50% off!

Additional Support Options: