gst
it is the responsibility of the business to collect the gst, the onus is not according to my information, on the customer. A recreational qualification such as a ppl attracts GST. The qualification that requires you to enter a profession such as a CPL is GST exempt. The additional qualification done after a CPL attracts GST. An instructor rating is a required qualification to enter that field so does not attract GST, whereas an instrument rating after a cpl cops gst but not if done as part of and prior to the cpl flight test.
Interestingly the 200 hour cpl cops gst but the 150 hour cpl does not.
If you enter a cpl course avoiding gst and pulled out prior to completion, then i believe there is no gst component.