California Code, Revenue and Taxation Code - RTC § 19518

(a) The trustee of a trust described in Section 401(a) of the Internal Revenue Code 1 which is exempt from tax under Section 17631 to which contributions have been paid under a plan on behalf of any owner-employee (as defined in Section 401(c)(3) of the Internal Revenue Code), and each insurance company or other person which is the issuer of a contract purchased by such a trust, or purchased under a plan described in Section 403(a) of the Internal Revenue Code, contributions for which have been paid on behalf of any owner-employee, shall file the returns (in the form and at the times), keep the records, make the identification of contracts and funds (and accounts within the funds), and supply the information, as the Franchise Tax Board shall by forms or regulations prescribe.

(b) Every individual on whose behalf contributions have been paid as an owner-employee (as defined in Section 401(c)(3) of the Internal Revenue Code)--

shall furnish the trustee, insurance company, or other person, as the case may be, the information at the times and in the form and manner as the Franchise Tax Board shall prescribe by forms or regulations.