In TurboTax Online, you can clear and start over as long as you haven't paid or registered yet (free users are asked to register their accounts before they file). More info: https://ttlc.intuit.com/questions/2586254-how-do-i-clear-and-start-over
If
you want to deactivate your account instead, you'll have to send a
message to Customer Service (they'll give you a case number and tell you
what to do next): https://support.turbotax.intuit.com/contact/
