California Code, Evidence Code - EVID § 1272

(a) It was the regular course of that business to make records of all such acts, conditions, or events at or near the time of the act, condition, or event and to preserve them; and

(b) The sources of information and method and time of preparation of the records of that business were such that the absence of a record of an act, condition, or event is a trustworthy indication that the act or event did not occur or the condition did not exist.