My son held a job over the summer as an independent contractor. TurboTax says he owes $1,200. When he enters his business mileage, the program lists $900 in job related expenses. Yet the $1,200 owed does not change.
Shouldn't it?
I suggest that you LOOK at the form 1040 before and after you enter the car expenses to see exactly what is being changed and how. If you still have questions post back with more details like form and line numbers.
You can view your entire return or just your 1040 form before you e-file: