How do I stop the previous year's data from transferring over to this year's tax form?

If you Clear and Start Over after you bring the information in it will clear all of the tax data, but leave your personal information.

1. On the menu bar on the left that shows.
   1. My Info
   2. Federal
   3. State
   4. Review
   5. File
2. Select Tax Tools
3. On the drop down select Tools
4. On the Pop-Up menu select Clear and Start Over
5. Caution:  Be sure that this is what you want to do.
6. Select Yes
7. This will complete the process.

Clear and Start over

There is a tricky way to clear out transferred info in the Online version. But doing this will also clear out all your entries. Go into your return, go Tax Tools > Tools > Transfer from your computer > Continue > then Continue without transferring.

Or you can just start a brand new account with a new username.

The Online version is only good for 1 return. But you can use the same email address for 5 accounts. To do another return log out of your account and set up a new account and new user name and pay any fees again. That's why it's better to use the Desktop CD/Download program. The Desktop program can do more than 1 return and efile 5 for free.

How to start another return in the Online version
https://ttlc.intuit.com/community/using-turbotax/help/how-do-i-start-another-return-in-turbotax-online/00/25596