If you are using the TurboTax online web based editions you need to create a new account with a new User ID to start another tax return - https://turbotax.intuit.com/personal-taxes/online/
If you are using the TurboTax desktop CD/Download editions with the software installed on your personal computer, to start a new tax return click on the File menu at the upper left of the desktop program screen. Then click on New Tax Return.
