Example
I am granted an employee stock option with an exercise price of $20 per share. I exercise the option when the shares are worth $25 each.
Later, I sell them for $28 each.
Result:
I have a $5 per share employment benefit, which is cut in half in computing taxable income assuming I meet the criteria discussed earlier.
My adjusted cost base of the shares becomes $25 (the $20 exercise price plus the benefit included in my income). So when I sell the shares for $28, I have a capital gain of only $3 per share, half of which is included in my income as a “taxable capital gain” (the normal rule for taxing capital gains).
Conversely, if I sell the shares for $22 per share, I would have
a capital loss of $3 per share, and half of that would be an allowable capital loss (generally claimable only against taxable capital gains).