You can’t. Online is only good for 1 return per account. But you can use the same email address for 5 accounts. You can start another return in TurboTax Online by:
- Logging out if you are in your account
- Choose what TurboTax Online product you want to use for the second return
- Create your account screen
- Set up a new login for the second return
- Start working on the new return
The Desktop program can do unlimited returns and efile 5. You can buy the Desktop CD/Download program directly from Turbo Tax
TurboTax® 2021-2022 CD/Download Tax Software, Compare Desktop Tax Preparation
