According to this turbo tax document, turbo Tax Tax will calculate the amount of deductible interest but to do so, turbo Tax will ask you a series of follow-up questions to make sure you're qualified to take the deduction. Usually these types of questions are unique to your mortgage information that is not reported elsewhere in your return.

Thanks. TT did ask me the questions referenced in your document, but it doesn't appear to calculate the adjusted deduction if the mortgage principal is >$750,000. TT did explain (much better than the IRS) how to adjust the deduction by hand.