There is no procedure to delete, close or merge an account since accounts may contain past tax information that needs to be preserved. You can just let it go dormant. To secure your account, log in to your Turbotax account by typing the address into your browser window, and make sure your browser shows a padlock icon or whatever symbol it uses to indicate a secure verified connection. Change your password, and make sure it is not something you use on other web sites. Change your security question to something that a crook could not guess from social media. Make sure your email address and cell phone number are up to date as Turbotax may use that to help verify future attempts to log in.
You also have the option to turn on 2-factor authentication for all log-ins. With 2-factor authentication, Turbotax will send a code to your email or cell phone when you try to log in. The idea is that only someone who knows your password and also has possession of your phone will be able to log in, this is more likely to be the real you. Turbotax will use 2-factor authentication whenever you log in from a computer that turbotax does not recognize, but you can turn it on for all log-ins in your security settings.
If you started an online return you can delete all your info and abandon it, if you wish. Your account will still be available for you to use at some point in the future, as long as you use the same User ID and password. You could also indicate that Intuit emails are spam to keep them out of your regular email.
