You can start your tax return over in TurboTax Online by using our clear and start feature as long has you haven't submitted payment, deducted the TurboTax fee from your refund, or registered, please see this TurboTax FAQ for more information:
https://ttlc.intuit.com/community/using-turbotax/help/how-do-i-clear-and-start-over-in-turbotax-online/00/26444