Earlier quoted context omitted.
Can you write off just the exercise price or the fair market value at time of exercise?
Confirm this with your tax advisor, but FMV at exercise is your basis in later years (generally because the difference in FMV and strike will have caused you a taxable event). c.f. https://www.untracht.com/news-insights/vantagepoint-newslett... Edit: Consider the case where this were not treated as true. You're clearly not going to pay $2 strike, exercise at $5 ($3 of employment income due to the bargain element), se…
For general information on this topic see https://www.irs.gov/newsroom/capital-gains-and-losses-10-hel...