I've been trying to understand a similar problem, and @TomYoung 's answer is helping straighten me out. Let me follow up and check my understanding:
The AMT credit and the basis adjustment appear to be two separate things. First, the basis adjustment. When I make a qualifying sale of stock acquired through exercise in a year I incurred AMT, the regular Schedule D is unaffected: the basis is the ISO strike price. But on the AMT Schedule D, the basis is the FMV, which will lower my AMT exposure from that sale. This calculation is not sensitive to how much AMT I incurred when I exercised or how much AMT credit I have - if I incurred AMT the year I exercised to buy that lot, the basis to use on AMT Schedule D is the FMV. Is that about right? Or are there subtleties I'm missing?
Now, the credit. When I'm done with all the calculations, if I have no AMT liability, I can start spending the credit. I can claim an amount equal to (regular tax minus AMT). Is that about right?
Any clarifications or corrections to my understanding will be welcome.
