You will not be able to file another person's return using your account. If you do so, you will overwrite your tax return information. To file an additional return using TurboTax Online,
you will need to create a new account. Please see the following TurboTax
FAQ for instructions on how to start another return using TurboTax Online.
https://ttlc.intuit.com/replies/3288574
If you have several returns to file, you may be interested in purchasing a TurboTax CD/Download, as you can e-file up 5 federal returns for no extra charge, whereas you will be charged for each return (unless eligible for free filing) using TurboTax Online.
