IBX Oppies, page-166

Not tax advice but...

Yes, if you buy an asset like options and they expire and you choose not to exercise then you claim a deduction (plus any change to the CPI cost base) against any other capital gain.

Options expiring is a CGT event regardless of whether you exercise or not. They are in effect a disposal of an asset. You either start a new purchase at the option exercise price, and log a disposal at the last market value, or dispose of them at $0 consideration.

So if you buy options at 5c to exercise at 10c and the option price is 20c when you exercise then you make a profit of 15c and pay CGT on that. And your new cost base for your heads is 10c. If the option price at exercise is 0c and you don't exercise then you log a 5c capital loss.