California Code, Revenue and Taxation Code - RTC § 19171

(a) A business entity required to electronically file a return pursuant to Section 18621.10 that files a return in a manner that fails to comply with Section 18621.10, shall be subject to a penalty in the amount of one hundred dollars ($100) for an initial failure and a penalty in the amount of five hundred dollars ($500) for each subsequent failure unless the failure is due to reasonable cause, and not willful neglect.

(b) If a group return is filed on behalf of eligible electing taxpayer members of a combined reporting group, the penalties described in subdivision (a) shall apply to the combined reporting group and not to a taxpayer member of the combined reporting group.

(c) This section shall apply to returns filed for taxable years beginning on or after January 1, 2017.