If you have logged in to TurboTax online, you are now in TurboTax for 2016 which cannot be used to file a 2015 tax return. Use this link to finish a 2015 tax return that was started with TurboTax online for 2015: https://ttlc.intuit.com/questions/2559403-how-do-i-finish-a-prior-year-return-that-i-started-in-turb...
