If you use TurboTax Online you have to have a separate user ID for each tax return. You cannot prepare more than one tax return with the same user ID. You sign in with the user ID of the return that you want to work on, and sign out when you want to switch to a different return.
See the following FAQ for instructions to start another tax return with a new user ID.
How do I start another return in TurboTax Online?
When you have to file multiple returns, it's usually less expensive to use the CD/Download TurboTax software. You pay for the software once and you can use it for multiple returns. There is an additional charge for each state e-file, but it still usually works out to be less expensive. The CD or download software also has features that are not available in TurboTax Online. The most significant feature is forms mode, which lets you look at the forms while you are working on the tax return, and even make entries directly on the forms.
