When do I pay AMT on exercise of ISO stock options?

[kris1980]

I exercised my ISO stock options (bought all the vested stock options) in September 2019. Now I have to pay 28% AMT on the different between the exercise price and the grant price. When is the last day for me to pay the AMT? Is it October 15th 2019. or April 15th 2020?

[fanfare]

AMT is paid on Tax Day 2020 along with all other taxes.

There is risk of penalties for not submitting Estimated Tax payments in 2019; this depends on how much tax you owe.

[kris1980]

Thanks Fanfare for replying.

Apart from AMT, I don't owe anything else. So I am assuming AMT does not fall in estimated-taxes category and hence I should be paying AMT by April-15 2020.