Generally, it is not necessary but it may be helpful and/or reduce additional work later. For example, you would refer to prior year tax return(s) for amounts that carryover, such as depreciation, capital losses, passive losses, etc. TurboTax usually asks questions about prior year tax return(s) so it would be better if you had the information available. Furthermore, you would need your prior year AGI if you wanted to e-file your current year tax return(s). Please review the following link(s) and the link(s) embedded on the webpage(s) for more information:
If you used TurboTax Online to file prior year tax return(s), please ensure
you are consistently using the same TurboTax Online account each time you sign
in and on each device you use. Many users have more than one account and don't
even know it. Several users also don't realize they are using a different
account each year. TurboTax Online accounts are differentiated by user ID and
e-mail address. Each years' tax return(s) are located in the TurboTax
Online account(s) used to file that years' tax return(s). Please review the
following link to verify how many accounts you have and note Step 4
"Repeat these steps for any other email addresses you may
have.": How many TurboTax accounts do I have?
If you used TurboTax CD/Download to file your prior year tax return(s), the files will be saved locally on the computer you used to file those tax return(s) (not in one of your TurboTax Online account(s)). Please review the following link(s) and the link(s) embedded on the webpage(s) for more information: