The Online product is only available for the current year
filing. To file previous years you will need to use the Desktop product. Please
click here to get started: https://turbotax.intuit.com/personal-taxes/past-years-products/.
This link has some helpful information
on filing previous years returns: https://turbotax.intuit.com/tax-tools/tax-tips/IRS-Tax-Return/How-Do-I-File-Back-Tax-Returns-/INF14505.html