If you have registered or it won't let you clear to start over and you haven’t paid, you can just abandon this account and start over with a new account. Online is only good for 1 return per account. How to start another return in the Online version
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
https://turbotax.intuit.com/personal-taxes/compare/online
Create your account screen
Set up a new login for the second return
Start working on the new return