It specified in the link that after you contact the support team and specify your request > they will email you the form privately :
Instructions for deleting your TurboTax online account
- Our team will email you a form to help confirm your identity.
- Contact our customer care team (click here: link) and let them know you want to deactivate your online account.
- Fill out the form.
Our security team will then be able to deactivate your account.
I hope this was helpful
