The TurboTax online editions are only for tax year 2017
See this TurboTax support FAQ for completing a prior year tax return started with the online editions - https://ttlc.intuit.com/questions/2559403-how-do-i-finish-a-prior-year-return-that-i-started-in-turb...
A 2016 tax return can only be printed and mailed, it cannot be e-filed.
