You can try to clear you return but you can not delete your account. How to delete/clear your Online return
https://ttlc.intuit.com/community/using-turbotax/help/how-do-i-clear-and-start-over-in-turbotax-onli...
If you want to completely deactive your account you need to call in and get a case number.
Contact Customer Service
5am-5pm Pacific Time Monday -Friday
https://support.turbotax.intuit.com/contact/
What is the Turbo Tax phone number
https://ttlc.intuit.com/community/using-turbotax/help/what-is-the-turbotax-phone-number/00/25632
