When you use Online TurboTax, you get one return per fee.
When you use Desktop TurboTax, which you install from a CD or download to your own hard drive, you can prepare and e-file multiple returns for the cost of the software. You can e-file up to 5 Federal returns—more if you mail the additional ones. If you have multiple returns to prepare for family members, Desktop is more cost effective.
Every return must have it's own userID and password ... you cannot use the same account for 2 people.