Thanks RaifH for your response. However, it does not address my concern. You are correct that the percentage of acquisition interest is calculated using the average 'total debt' and 'acquisition' balances. However, for mixed-use mortgages, the averages must be calculated by summing the monthly balances and dividing by 12 instead of using the beginning and ending balances and dividing by two.
My issue is that Turbo Tax did not use an average at all for my mixed-use mortgage. Instead, Turbo Tax appears to be dividing the ending 'acquisition debt' by the ending 'total debt' to figure the percentage of deductible interest. In addition, Turbo Tax does not appear to round the percentage to three decimal places as required by Pub 936.
I say 'appear' because this is the only way I can come up with the same value Turbo Tax does.
