If you are using TurboTax Desktop, you can start either return. TurboTax Desktop allows you to file up to five returns, but you can "Start" even more.
Each return in the Desktop program is saved as a file. You can start one, save it, then switch to another. You may then later return to a file you have in progress.
If you are using TurboTax Online, do NOT use the same account for more than one return. You may use the same email address, but will need to set-up usernames and passwords for each Taxpayer.
HERE is a link for How to file more than one return using TurboTax Online.
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