I made an error on CA Form 5805 and simply wish to start over on that form. How?

Try this:

 

For Online users:

On the left, click on Tax Tools, then click on Tools underneath it, then click on Delete a Form in the center. Scroll down to delete the 5805.

 

For CD/download software users:

Click on Forms on the upper right, scroll down the list on the left to California, locate form 5805 and click on it to view it, and at the bottom of the view pane, there is a Delete button.

The Form 5805 is a pain to fill since it doesn't really tell you what you're doing when it simply says to enter Part III, Line 1 - There are 4 Line 1 entries.  And you don't know how they're handling it until it's done and unchangeable.  Not great.