I have the same issue.
Turbotax should include the limit or limited amount calculations. It is supposed to be a tax calculator. The user should not be required to do such hand calculations.
Can Intuit issue an software update, to include this calculation, now?
Another issue is this may come from the fact that I entered 2 mortgage lenders, because these lenders sell mortgages with the mortgage payer packaged, bank to bank. Then 2 lenders show up on my return, as if i had purchased 2 homes for a total of 2x amount. Lenders buying and selling ongoing mortgagees is so common, mine was sold 4 times in 5 years. Turbotax should handle that in the step by step guide.
What the IRS publication says, if I understand it correctly:
If you bought your house before 2017, and your mortgage amount is less than $1M, then you can deduct all the mortgage interest you paid. Meaning the line match with the line above it. For example if you bought it in 2016 with a $1.2M mortgage, then you have to calculate the mortgage interest amount portion of the $1M portion of the $1.2M mortgage, and enter that. For purchased after 2017, the limit is $750k mortgage amount, to qualify for full amount of MI to be deducted.
I'm not a tax expert, not even close.
