TurboTax online accounts cannot be deleted. You can remove all the information from the tax return and then just abandon the account if you do not want to complete and file a 2017 tax return using the TurboTax online editions.
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 2017 online tax return. Click on Clear & Start Over.
