Review the entire return ... the fed tax is only part of the equation : 

You can peek at only the form 1040 & state summary page  by going here:

Click on Tax Tools >>>Tools >>>Click on View Tax Summary >>>Click on Preview my 1040

To view the entire return using the online editions before you file, you will need to pay for your online account.

To pay the TurboTax online account fees by credit card, without completing the 2017 return at this time, click on Tools … Then click on Print Center.  Then click on Print, save or preview this year's return.  On the next page, to pay by credit card, click Continue.  On the next screen it will ask if you want Audit Defense, if you do not want this option just click on the Continue button.  The next screen will ask for all your credit card information so you can pay for the account.

Are you self-employed (1099 or cash)?  If so, you are subject to approx. 15% Federal self-employment tax, as well as regular income tax.  Or, you may be paying a tax penalty of some kind, such as for the early withdrawal of a retirement plan.