I exercised and held ISOs this tax year with a significant exercise price/FMV difference. The sale wasn't reported on my W2, but I filled out the "ISO Exercise and Hold" section in the EasyStep view. In the form view, none of this AMT taxable difference shows up in 6251/6251 Wks forms, and the Exercise SO Worksheet is blank in the 4 - Alternative Minimum Tax (AMT) Summary section.
From everything I understand about AMT and ISOs, this is an AMT-taxable event. Is this a bug, a not yet released functionality, or am I missing something obvious?
Yes, it is. Two things spring to mind. First, you said significant. If the amount is over $100,000 there are more implications. The portion over $100,000 is treated differently- as NSO You can see IRS sec 422(d) for more. Secondly, the 6251 has not been released so the program isn't capable of handling it correctly until the form is released by the IRS. The state and federal governments approve the most common forms first and work their way down the list. Please see the links for form availability. Once a date shows up, the reality should be close. Once released, Turbo Tax will work quickly to get it working in the program.