After you file

If you forgot to pay your federal tax due, you will be billed later by the IRS for the interest you owe.  That will be calculated by the IRS based on how much you owed and when they receive the payment for the amount due as shown on your Form 1040--line 37.  TurboTax will not do that calculation.

**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**