Cal. Rev. & Tax. Code § 12003

“Insurer” as used in this part includes each of the following:

(a)Insurance companies or associations.

(b)Reciprocal or interinsurance exchanges, together with their corporate or other attorneys in fact considered as a single unit.

(c)The State Compensation Insurance Fund.

As used in this section, “companies” includes persons, partnerships, joint stock associations, companies and corporations.