When using the online versions, you will have to start a new account with a new
unique user ID for another tax return. The online editions are only good for
completing one tax return per account and user ID.
https://ttlc.intuit.com/replies/3288574
When you use Desktop version of Turbo Tax, you can prepare and e-file up to 5 Federal returns for
the cost of the software plus one free state filing.