According to several posts on this topic, Turbotax supposedly calculates an effective tax rate by dividing Total Tax (1040 Line 26) by Taxable Income (1040 Line 11b). However, when I use the numbers on those lines and calculate my effective rate, I wind up with a rate of 19.8% vs the Turbotax summary page calculation of 17.79%. Why does Turbotax underestimate my effective rate?
