I want to delete my account.

We don't really cancel your account, but you can remove the data.   We will keep the username and password you created in case you ever want to return to the website. 

If you would like to erase the data you have entered, you can do that by following these directions:

1. While in your TurboTax Online program (after clicking Continue your return)
   Select My Account.
2. Then click on Clear & start over.
3. On the Are you sure you want to clear your return? pop up screen, if you are sure about clearing all your entries and starting over, click Yes.
4. Then a new screen confirms you have cleared your entries, click Continue.

All of your entries will now be erased.

you would have to contact product support. When there let them know that you want to delete the account, there they will submit a form that will render that current account not active. So now one will be able to enter it again.

https://ttlc.intuit.com/replies/3300041?