A TurboTax Online account can only be used for one federal tax return. To do a tax return for someone else, you have to use a different account. You cannot prepare another tax return with the same account that you used for your own return. You have to pay for each account separately.
When you have to file multiple returns, it's usually less expensive to use the CD or 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.
See the FAQ at the following link for instructions to start another tax return with a new account.
https://ttlc.intuit.com/questions/1894512-how-do-i-start-another-return-in-turbotax-online
If you are a paid tax preparer, you cannot use TurboTax at all, either Online or CD/Download. TurboTax is only for consumer use. Intuit (the company that makes TurboTax) has three tax software product lines for professional preparers: ProSeries, Lacerte, and ProConnect Tax Online. You can find information about all three product lines at the following link.
https://proconnect.intuit.com/
If you have a small practice with primarily individual clients, you will probably find ProSeries Basic to be most suitable.
