Tax liability regarding ISO options given to employee



Hi All,

I am working in a startup company. This question is related to tax liability for ISO stock options.

Our company offered Qualified Incentive based Stock Options (ISO) when I joined. As this startup HQ is
in US, the grant price is in $. Lets consider the grant price as “G” $. My stocks are vested now.
But the current fair market value is “F” $. If I buy this stock, should I pay the tax for the “F - G” $ under

Please note that share doesn’t have any real value as there is no buy back option and also I can’t sell it
in the market. If the company doesn’t perform well, then it would be a huge loss for me (“F - G” is significant).
Should we really pay the tax for the non-tradable/non-payback stock options (which doesn’t have real value
as of now)? Is there any option to pay the tax when I sell the stocks (i.e when the stock would have any value).

Please advice.