If you haven't paid, registered, or filed yet, you can wipe all transferred data and start from scratch.
TurboTax Online: In the left menu, select Tax Tools, then Tools. Choose Clear & Start Over in the pop-up and confirm with Yes.
TurboTax Mobile App: Select More from the bottom menu, then Clear and Start Over.
TurboTax Desktop: Go to the File menu and select New Tax Return to start a clean file without transferring.