Unfortunately, you cannot delete an account. You can, however, call in to the help desk and an agent can help you deactivate your account. Here is how to reach TurboTax.
https://ttlc.intuit.com/replies/3300041
If you are wanting to simply delete all your information from your taxes on TurboTax, you can use the Clear and Start Over function.
https://ttlc.intuit.com/replies/4248526
