@GSD77 - while I haven't run though how TT is doing this, for simplicity combine mortgages where the loan was simply transferred to another servicer. How many mortgages do you then have?
the 'average loan balance' is the interest on THAT mortgage divided by its interest rate. So that if you paid off a mortgage during the year or originated one, the result will weight for that. A two point average will skew results.
https://www.irs.gov/pub/irs-pdf/p936.pdf
see page 13 at the middle top.
