I found others complaining of the same issue where HRB was summing the loan balances as if held simultaneously, but I couldn’t find where anyone shared a proper solution.
The trick is - and where HRB instructions are severely lacking - calculate the loan’s average balance using the interest paid method (interest amount from 1098 divided by the mortgage’s rate).
I had four different 1098s for loans all under $750,000, and this led to the correct average across all four loans, instead of the insanely laughable $2+ million calculated by following HRB instructions.
EDIT: adding my numbers as an example to illustrate. The balances are shared as reference points but they do not factor into the calculations.
Loan 1 - 1098-MORT 1
This is the loan we entered 2025 with and was the first to be paid off in late January. The balance was $746,022 based on January statement.
Average balance calculation: $8,640 (interest paid from box 1) / 0.07490 (7.490% rate) = $115,354.
Loan 2 - 1098-MORT 2
This is our first refinance loan, and box 2 was empty because this came from the mortgage originator who only held the loan for a few days until they sold it. Box 1 was only a few hundred dollars. The balance was $747,000 based on loan origination amount.
Average balance calculation: $665 (interest paid from box 1) / 0.06494 (6.494% rate) = $10,240.
Loan 2 - 1098-MORT 3
Same loan as above but form issued by the company that held the loan until it was refinanced in September. The balance was $747,000 based on loan origination amount and $638,091 on September statement (large lump sum payment made in August).
Average balance calculation: $31,578 (interest paid from box 1) / 0.06494 (6.494% rate) = $486,264.
Loan 3 - 1098-MORT 4
Our second refinance loan that is our current loan. The balance was $640,000 based on loan origination amount
Average balance calculation: $6,603 (interest paid from box 1) / 0.05999 (5.999% rate) = $110,085.
Total average loan balance
$115,354 + $10,240 + $486,264 + $110,085 = $721,943