Yes, Turbo Tax assumes the mortgage limitation is based on the original mortgage date and not on the the refinance date since Pub 936 does not specially say otherwise. When entering the 1098 for your current refinance, Box 3 will have the refinanced date. That's okay. If you checked that this loan is a refinance of a previous loan, Turbo Tax will ask you for the date 'the home was purchased by 'refinance lender name' when you complete and click Done on the 1098 page. Enter the 2015 date of the original mortgage.
