I agree: following the step-by-step prompts results in a doubling of the AMT adjustment. The step-by-step prompt under Personal Income / Investment Income / ISO Exercise and Hold seems to work correctly, having one enter the Form 3921 information manually. However, under Other Tax Situations / Alternative Minimum Tax, the prompting asks, "Do you have any of these uncommon situations? Select all that apply to your 2024 taxes." Answering truthfully, one checks "I exercised ISOs in 2024, but didn't sell the stock in 2024. Or I sold ISOs in 2024 that I purchased in a previous year." This leads to a prompt, "OK, let's get the info for your incentive stock options (ISOs) ... Enter your ISO adjustment." So, if you enter a manually calculated value correctly, it puts a doubled value in Form 6251 Line 2i. Drilling down on that value into Form 6251 AMT Worksheet, the manual value shows up in ISO Line 4, while the (same) value shows up in Line 3, which is automatically populated by the first entries in ISO Exercise and Hold (above). IF one happens to click on Help Center WHILE in Form view, then the explanation for Line 4 comes up:
Incentive Stock Options - Line 2i Worksheet
Line 4:
Enter an amount on line 4 if the taxpayer was granted or exercised an additional incentive stock option that was NOT entered on a Schedule K-1 Worksheet for Partnerships or on the Stock Option Worksheet. (If this is the case, you must manually calculate the excess AMT income over regular tax income.)
If that *NOT* statement were put in the step-by-step prompting, this extremely costly problem would be avoided. (For my return, doubling would cost me $9500.)
