If you file late the California Franchise Tax Board will put you in the penalty box!
The penalties can add up if you file late or fail to file a California income tax return. Late penalties associated with certain business entities can really add up. For example:
Late Filing Penalty - Partnership and Limited Liability Company Treated Like Partnerships
The FTB will impose a penalty if you fail to file the business entity's tax return by its due date. For tax returns filed before January 1, 2011, the penalty is $10 per partner or member for each month or part of the month the tax return is late, not to exceed five months. For tax returns with original due dates on or after January 1, 2011, the penalty is $18 per partner or member for each month or part of the month that the failure continues, but not to exceed 12 months. (R&TC Section 19172).
I have seen this penalty assessed for over $1,000,000 for a single business entity return. I have also seen this penalty waived.
Late Filing Penalty - S Corp Shareholder
The FTB will impose a penalty if you fail to file the business entity's tax return by its due date. The FTB will impose the penalty for tax returns with original due dates on or after January 1, 2011. The penalty is $18 per shareholder for each month or part of the month that the failure continues, but not to exceed 12 months. (R&TC Section 19172.5).
Check out this link for other late filing penalties:
https://www.ftb.ca.gov/businesses/Penalty-Information.shtml