see below extract from Google mate: (winnings from sports betting is tax-free in Australia)
Gamblers’ winnings in Australia are not taxed. There are 3 main reasons for that: Gambling is not considered a profession, it’s treated as a hobby or recreational activity. The Australian government views gains from gambling activities not as income, but as a result of good luck.
Make sure you have have you Bank statement as verification for all bookmakers and sign up with Betfair First as this takes the longest to verify in my opinion.
Also, I suggest doing sign ups first too get the bank rolling steadily!
Once you have finished sign ups then get onto daily offers. These guys are pretty good at updating daily plays!
Good luck and feel free to ask more questions!