TurboTax online accounts cannot be deleted.
You can clear your return and all the tax data then just abandon the account.
If you have not paid for the online edition you are using, have not filed your tax return or registered the Free edition, then you can clear your return and start over. Click on Tax Tools on the left side of the program screen while working on the 2018 online tax return. Click on Clear & Start Over.
Online accounts can be deactivated so no one can access the account. To have the account deactivated you will need to contact TurboTax support.
Use this website to contact TurboTax support during business hours - https://support.turbotax.intuit.com/contact/
Support can also be reached by messaging them on these pages https://www.facebook.com/turbotax/ and https://twitter.com/TeamTurboTax
