Once the GST is turned on in QBO it cannot be turned off. However that does not stop you from moving to a non GST reporting option.
The easiest way to do this is to go into the Company Settings area – Gear icon top right corner.
Advanced tab> Default Tax rate […]

Resolution for 'au accounting banking taxes issue: 'AU I have de-registered for GST, how do I reflect this change?' available: Yes.

The au accounting banking taxes 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 au accounting banking taxes issue yourself by looking for a resolution described in the article. If it is a complex au accounting banking taxes issue or you are unable to solve the issue, you may contact us by clicking here or by using other au accounting banking taxes support options.

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