Form 6251 and Form 8801 explained
Form 6251 calculates AMT. Form 8801 recovers the credit. Both show up on returns with ISO activity.
Form 6251
This is where the ISO bargain element is added back to income, the exemption is applied and tentative minimum tax is computed. Your broker's Form 3921 supplies the exercise data you need.
Form 8801
Form 8801 tracks the minimum tax credit carryforward and claims it in years when regular tax exceeds tentative minimum tax. Missing this form is the single most common way people lose AMT they already paid.
Dual basis records
ISO shares carry one cost basis for regular tax and a higher one for AMT. Keep both permanently — you need them for every future sale, sometimes a decade later.
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