If you are using the Online version, you would have to do a new, separate online account (with a different user ID) for each federal return you want to prepare and purchase for each (if you need to use a paid version of the online software). If you do another return under the same username, it will override the one you already filed and lose everything for that return.
- Start another return in TurboTax Online: https://ttlc.intuit.com/questions/1894512
You can still use your same email address (for up to 5 online accounts) if you want to get notifications, but the username must be a new one for each online account you create.
The CD/Download (desktop version) product is a better overall value for people who prepare tax returns for their friends and family. This one will allow you to prepare and print unlimited federal returns and e-file up to five at no extra cost. You can find the desktop versions here https://turbotax.intuit.com/personal-taxes/cd-download/