You can file a paper return for 2015 using
TurboTax CD/Download for Windows or Mac. Simply
purchase the software and install it on your computer. You’ll need to print and mail your return.
TurboTax CD/Download is available for the three years previous to the current tax year.
TurboTax Online is not available for prior-year tax returns.
https://ttlc.intuit.com/replies/3301607
https://turbotax.intuit.com/tax-tips/irs-tax-return/how-do-i-file-back-tax-returns/L535BxMms
https://turbotax.intuit.com/personal-taxes/past-years-products/2015/
