Yes, a single member LLC (SMLLC)that is disregarded for federal income tax
and files Schedule C does file CA Form 5668.
From the form:
"Disregarded entities that do not meet the filing requirements to complete Schedule B or Schedule K should prepare Schedule IW by entering the California amounts attributable to the disregarded entity from the member’s federal Schedule B, C, E, F (Form 1040), or additional schedules associated with other activities."
Every SMLLC doing business in California must file its own return, and pay its own $800 annual tax
and LLC fee based on its own income.
See instructions on page 13 of the Form 568 Booklet for more information on how to complete Schedule IW.
Please ask if you need more discussion or clarification.