I stumbled upon this discussion and thought I would add my 2 cents.
This link to some ATO guidance will be useful for answering your question: https://www.ato.gov.au/printfriendly.aspx?url=/Business/Bus/Property-and-Construction-Industry-Partnership—issues-register—section-01—bodies-corporate-owners-corporations-and-strata-managers/#1.1.1
In brief, strata body corporates (or Owners Corporations) must be registered for GST if their turnover exceeds AUD75,000 in any 12 month period (NOT AUD150,000 as the ATO does not generally consider Owners Corporations to be not-for-profits).
This means there will be an obligation to lodge quarterly business activity statements and charge GST on levies. However, at the same time, your Owners Corporation will also now be able to claim any GST on costs (e.g. maintenance, contractors, electricity etc). Your strata manager should be able to advise on how this should affect your budget.
The fact that Owners Corps have been “dragged” into the GST net by the ATO’s interpretation is unfortunate and probably should have been excluded outright (this is the case in other jurisdictions with a value added tax or similar).
Hope this and the link to the ATO website helps.