In TurboTax Online, you can file one (1) federal return per account/user ID. You may have up to five (5) User Id's using the same e-mail address.
In the TurboTax
CD/Downloads you can e-file up to 5 federal returns and create an unlimited number of returns to mail.
For additional information please see the following TurboTax FAQ. https://ttlc.intuit.com/replies/4883581