How will the ATO know whose wallet belongs to who?

I am 19 and never had to do taxes until this financial year, so I'm a bit confused.

How will the ATO know what transaction is considered a "gift"? Say I bought 1 bitcoin on exchange A and transfer 0.5 to wallet B, which I own. The other 0.5 is transferred to wallet C, which is owned by my friend. How will the ATO know that I own wallet B but not wallet C?

I'm asking because I understand transferring from an exchange to your own wallet is not a taxable event, whereas transferring from an exchange to someone else's wallet (gifting) is a taxable event, however don't understand how the ATO will know whether a transaction is simply transfer to hard wallet or a gift.

Thanks!

edit: will I have to file a tax report and this is how they will know? i know that websites like koinly track your portfolio across different wallets whether that be exchanges, hard wallets etc.