@RaifH
OK, an update - I just tried your method from here again, but this time I used the average balances calculated from the interest rate method, into the TT online prompt for "Box 2 - Outstanding mortgage principal". I came up with the exact same deduction as my independent Excel calculation. So that's a good sign.
Is there a possible concern that the amounts I'm entering aren't ACTUALLY the "Box 2 - Outstanding mortgage principal", but rather the average annual balances for each mortgage? Am I going to get audited for mis-entering entries on my 1098? Or it's fine because the numbers match the instructions from the IRS in the end?
