This concerned me too when I started using TurboTax many years ago. Notice when you begin the process of answering questions your 'tax due' and 'tax refund' amounts are zero. TT doesn't calculate anything until you answer questions (yes/no included) or input data. Each question can raise or lower the amount you owe. It's common to see the amount you owe go up when you answer questions. What I do these days is skip ahead and check the standard deductions box and check AMT before filling out the whole form. That way I know my baseline for what I owe (or my refund) before getting in the weeds.