If you already e-filed, you cannot cancel it. It is just like putting an envelope into a mailbox on the corner. You cannot get it back. If you e-filed with mistakes or forgot to enter something, you will have to wait to see if the return is rejected or accepted. If rejected, you can make corrections and re-file. If it is accepted, you have to wait for the IRS to process it and then amend to make corrections.
If you have not e-filed, you can clear out your data and start over--or just clear it and do not "start over."
CLEAR AND START OVER
https://ttlc.intuit.com/questions/2586254-how-do-i-clear-and-start-over
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**