Is your new mortgage for number of days outstanding 362/365 times amount plus 3/365 times amount less than 750000. I would use the calculated amount for beginning and use actual of new mortgage as beginning and ending. Name for each mortgage holder that is, bank 1 and bank 2 and combine interest amounts as one loan and hopefully will work. Also if combined over 750000 I think it will also work, but interest deduction will be limited. You should be able to calculate on excel or piece of paper to see if amount is right. If less than 750000: obviously 100% of interest deductible.
