Investors & landlords

Thanks for the reply.  Can you or anyone explain or understand how the issue of double taxation is handled?

 

Say I exercised options in 2017 with valuation of $10.  Exercise price was $1.  So I paid AMT for $9 profit.

 

 

Now in 2020, the stock is worth $20.  If I pay $19 profit, I will be paying for initial $9 gain twice.  That does not sound right even if may be legal.