You don't have to override the software, but TurboTax will not do the calculations for you. You will get a screen that tells you to refer to IRS Publication 936 to calculate the amount of mortgage interest you can deduct, and there is a box on that screen to enter the amount that you calculate. This appears to be a deliberate design decision that TurboTax is not going to handle the more complex mortgage deduction calculations. We've asked the forum moderators about it, but I don't think they are going to add those calculations to the software. My guess is that there are not enough TurboTax users with mortgages over $750,000 to make it worth the extensive programming effort that would be needed.
