Suppose in May 2023, I sell-to-open an AAPL option and receive $500. I believe this is a CGT event D2, treated as a capital gain of $500 for FY2023.
Now in Jan 2024, I buy-to-close that option, paying $400. This will be a CGT event C2.
Now the rule under subsection 104-25(3) of the ITAA 1997 says "you make a capital gain from CGT event C2 if the capital proceeds from the ending are more than the asset’s cost base. You make a capital loss if those capital proceeds are less than the asset’s reduced cost base."
My question is: what is the (reduced) cost base in this case? And so what capital gain or loss do I record in Jan 2024?