It sounds like you did not start out using the same account and user ID that you used for 2017, or you would have already had access and would have been able to transfer the 2017 information in to 2018 at the beginning. Now you want to get to your 2017 return? You say your 2018 return is not yet complete--you could consider starting over using the same account and user ID so that you could transfer 2017 in to 2018 That way you would have the 2017 AGI you are going to need in order to e-file 2018, and your personal information and some of your income information would also transfer in.
.https://ttlc.intuit.com/questions/1901535-forgot-your-turbotax-online-user-id-or-password
https://ttlc.intuit.com/questions/3404575-how-do-i-access-my-prior-year-2017-return
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**
