The penalty and interest are not calculated until the IRS receives the tax return and the payment due as shown on the Form 1040. TurboTax has no way to know when the IRS will receive/process your late mailed return nor does TT ever know if you paid your tax due--even the amount on line 37.
**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.**
