TurboTax is no longer available for 2013 and 2014.
You cannot use TurboTax Online to file for 2015. TurboTax Online is only for the current tax year, which is now 2018. To file for 2015 you have to use the CD or download TurboTax software for 2015. You can purchase a download at the following link. There is no free filing for past years.
https://turbotax.intuit.com/personal-taxes/past-years-products/2015/
To file for 2013 and 2014 you can look for other software that is still available for those years, or download the forms and instructions from the following link on the IRS web site and do it manually.
Prior Year Products
Tax returns for past years cannot be e-filed. You have to print the returns, sign them, and file them by mail. Mail each year in a separate envelope.
You can file tax returns for 2013, 2014, and 2015, but it's too late to get a refund for those years. If one of the tax returns shows a refund, you will not get the refund. If it shows a payment due, you have to pay the amount due.
