In the past, for every warrants I've exercised (not POET warrants).
I had to pay taxes on capital gains, which means:
I had a 0,10$ warrant
I exercised the warrant a specific day while the share price was 0,20$
I had to declare a 0,10$ capital gain even though i didn't sale the share the same day I've exercised.
Regards,
Note: Correct me If I was wrong