I don't have any experience with incentive stock options but you likely found a program error. I found one on my return this year relating to a K1 issue which had I not caught before filing, would have cost me over $2,000. The error occurred after an update which means they were trying to fix something else and inadvertently caused the program error. The most frustrating aspect of this is how Turbo Tax loves to continue to tout their 100% calculation accuracy but are eerily silent when an error like this occurs as no one addressed my concern when I posted it several days ago. Best course of action I found was to override the necessary fields to reach the proper tax outcome. Feels odd to do so but it was the only way I could get the correct calculated taxes.
