TurboTax accounts cannot be deleted. See this TurboTax support FAQ -
https://ttlc.intuit.com/community/using-turbotax/help/can-i-delete-my-tax-return-in-turbotax-online/...
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 2018 online tax return. Click on Clear & Start Over.
