Capital losses on underwater stock and options
Losing value on exercised shares and losing value on unexercised options are treated very differently.
Exercised shares
Selling below your basis creates a capital loss: offset capital gains, then up to $3,000 of ordinary income, then carry forward.
Unexercised options
Letting an underwater option expire generally produces no deduction. There is no basis to lose.
ISO shares and AMT
If you paid AMT on an exercise and the shares later crash, the loss is capital but the credit remains — recovery is slow. This is the core risk of exercising and holding.
This article is educational and not tax, legal, or financial advice. Talk to a CPA or tax advisor about your specific situation.