You wrote: E-file
Yes, a 2018 return can be efiled with TurboTax. Prior-year returns have to be printed, signed, dated, and mailed.
I need to E-file my 2018 taxes. I accidentally selected to mail in return. However I would like to E-file what steps do I need to take to do this?
How to change from Mail to Efile
https://ttlc.intuit.com/community/e-file/help/how-do-i-change-from-mail-to-e-file-in-turbotax-online/00/26985