I sold just enough shares to cover the cost of buying the stock. The 3921 has the total number of shares in the option as the number of shares transferred. However, the number of shares I'm holding is the number of shares in the ISO grant minus the number of shares to cover the cost of buying the shares. Also, it seems like the fair market value of the shares, on the data I acquired them, will be used to calculate my AMT. As such, it looks like I will owe a large amount of AMT (about an additional $40,000). Can I send a payment to the IRS to cover the additional tax and avoid a penalty? I have already sent my quarterly estimated tax payments for 2018.
