I did not use online versus in 2018. can I upload my 2018 from a file on my pc for 2019?

[DoninGA]

Yes, you can transfer the 2018 tax data file from your computer to the 2019 online editions when they become available.

See this TurboTax support FAQ for transferring to an online tax return - https://ttlc.intuit.com/community/entering-importing/help/how-do-i-transfer-last-year-s-return-into-...

[VolvoGirl]

Yes you can transfer from the prior year that's on your computer.  Are you talking about transferring into next year 2019 Online version?  Or to transfer into 2018 online that is due now in 2019?

If you used the Desktop program last year here’s How to transfer into the Online version, expand the blue link if you used the CD/download last year........

https://ttlc.intuit.com/community/entering-importing/help/how-do-i-transfer-last-year-s-return-into-...

If you used the Desktop program before you may not like the online version.  It has less features and no Forms Mode.  You can only do 1 return.  Your return is only saved online so be sure to save both the .tax2018 data file and the pdf file to your computer when you are done.  In case you need to amend in the future or if you need a copy to get a loan or something.  You might not be able to access your online return when you need a copy.