Mike9241 has the correct answer regarding how TT calculates the ETR. It appears that TT doesn't follow the standard formulas for this calculation. TT DOES use AGI to calculate ETR, but the tax used for the calculation is from line 22, not the total tax from line 24. I was able replicate TT's ETR following Mike9241's answer. As others have pointed out, line 22 is only income tax, whereas line 24 includes other payroll taxes, including self-employment tax. For most working people, the actual level of taxation is best calculated from line 34 (total tax) divided by AGI. That gives you the actual percentage of your income that goes to Federal income and other taxes. The difference can be quite large. In my case, TT calculated an ETR of 9.43%. But using line 34 divided by AGI, the tax rate was 17.17%. I did not report any substantial interest or other income; it's all pension, social security, and contractor income. That makes the 17.17% total more accurate.
