Will you shut down TurboTax before I file my taxes? What happens to all my work?

[DoninGA]

You can e-file a 2018 tax return using the TurboTax online editions up through October 15, 2019.  After that date the 2018 tax return can only be printed and mailed.  The TurboTax online editions for 2018 will be shutting down after 10/15/19 so the TurboTax desktop editions can be used to complete, print and mail a tax return.

[SteamTrain]

...and if you cannot get it e-filed before 15 October, then make sure you download your ".tax2018" datafile from your Online account.  That tax file is what contains all the information you have entered so far, and will be needed to continue working on your 2018 tax file using the desktop software.  (A PDF is useless for continuing to work on it.  It must be the datafile).  You should probably download the datafile even if you do get it e-filed by the deadline, just in case you do have to followup with some error, or later have to amend the tax file with the desktop software at a later date.

AND Get that file downloaded to your home computer before 25 October.  Sometime in the days/ few weeks following 25 October (unknown exactly when), the Online software will lock you out of accessing anything in that Online account for a few weeks.  Generally they will open it back up for access in late Nov or mid-late December, but you can't even get your ".tax2018" datafile during that lockdown period.

[KlisterKid]

Maybe it is time to buy the TT software on a CD! 🙂 I have helped a friend file returns that are over two years late by giving him my CDs to copy onto his computer. I have no idea what penalties he had.

If you don't have any CDs, search on the net for someone selling previous years' CDs.