If you have taxes owed, you have until April 18, 2017 to e-file or print your tax return and pay the taxes owed.  You can file an extension, Form 4868, which would give you an extra 6 months to file the 2016 return but the taxes owed are still due on or before April 18, 2017. 

If you have a tax refund you have up to three years from the April 18, 2017 due date to file your tax return for a refund.  There are no penalties for filing a tax return after the due date for a tax refund.

The 2015 AGI is only needed to e-file a tax return.  It is not needed to print and mail a tax return.  You can e-file a 2016 tax return using TurboTax until October 16, 2017.