Best to consult your tax accountant, but from ATO:
https://www.ato.gov.au/Forms/Guide-to-capital-gains-tax-2022/?anchor=Exercisingrightsoroptionstoacquireshares#ExercisingrightsoroptionstoacquiresharesCGT discount on shares or units acquired from exercise of rights or options
You can use the discount method to calculate your capital gain from an asset only if you own it for at least 12 months. In calculating any capital gain on shares or units you acquire from the exercise of a right or option, the 12-month period applies from the date you acquire the shares or units (not the date you acquired the right or option).
