I have completed my return but haven't filed yet. I did not have my 2017 taxes when I started but now have them. I would like to add that data so it comes up in my historical list when I file. How can I now add it?
TurboTax cannot merge accounts, so you would need to go to the 2017 account and do the 2018 return there.
Then you would have historical data.
I would leave it as is however look over 2017 and 2018 together to make sure nothing is overlooked on the 2018 based on 2017 data.