Cal. Rev. & Tax. Code § 19133

If any taxpayer fails or refuses to furnish any information requested in writing by the Franchise Tax Board or fails or refuses to make and file a return required by this part upon notice and demand by the Franchise Tax Board, then, unless the failure is due to reasonable cause and not willful neglect, the Franchise Tax Board may add a penalty of 25 percent of the amount of tax determined pursuant to Section 19087 or of any deficiency tax assessed by the Franchise Tax Board concerning the assessment of which the information or return was required.