How can I cancel my user with turbotax?

[DoninGA]

TurboTax accounts cannot be canceled or deleted.  You can clear any tax data from the 2019 tax return and 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.  Click on Tax Tools on the left side of the program screen while working on the 2019 online tax return. Click on Clear & Start Over.