@ pradyiitm
Do you happen to have any foreign earned income and used the Foreign Earned Income Exclusion? That can increase the tax on the non-excluded income.
TurboTax often uses other tax calculation worksheets aside from or in addition to the Tax Tables, depending on the circumstances in the return. Here's how to check:
If you are using Online TurboTax, here's how to look at your Form 1040 prior to paying, where you can also see a box as to what method(s) TurboTax is using to calculate your tax.
With your online return open, go to the left menu column and click on TAX TOOLS, then TOOLS.
In the Tools window, choose VIEW TAX SUMMARY.
When at the Tax Summary screen, go back to the left menu column and choose PREVIEW FORM 1040.
While previewing the Form 1040, scroll down to Line 15.
Just below Line 15 is a Tax Smart Worksheet that shows the methods TurboTax has used to calculate the tax.
