You asked where the amount of tax on Form 1040 line 44 comes from. You didn't say why you think it's not correct. There are seven different methods that can be used to calculate the tax, depending on what is in your return. As the form says, "see instructions." In the 2014 IRS instructions for Form 1040, look at the instructions for line 44, starting at the bottom of the middle column on page 40, where it says "Use one of the following methods to figure your tax." The seven methods are explained there. If your copy of your 2014 return includes all the worksheets, there is a Tax Smart Worksheet near the end of the federal return. One of the seven checkboxes in the Tax Smart Worksheet is checked to show which of the seven methods TurboTax used to calculate the tax on line 44.
