California Code, Business and Professions Code - BPC § 21605

(a) Every junk dealer and every recycler in this state is hereby required to keep a written record of all sales and purchases made in the course of his or her business.

(b) For purposes of this article, “recycler” means any processor, recycling center, or noncertified recycler, as those terms are defined in Chapter 2 (commencing with Section 14502) of Division 12.1 of the Public Resources Code, who buys or sells scrap metal that constitutes junk, as defined in Section 21600.