See this TurboTax support FAQ for when access to the online tax returns expire - <a rel="nofollow" target="_blank" href="
https://ttlc.intuit.com/questions/3355524-when-does-access-to-my-prior-year-turbotax-online-returns-...>
If you used and paid for the 2016 Deluxe online edition, then you had access to all online tax returns through October 2018.
