California Code, Civil Code - CIV § 3045.3

A lien shall not be effective, however, unless a written notice containing the name and address of the injured person, the date of the accident, the name and location of the hospital, the amount claimed as reasonable and necessary charges, and the name of each person, firm, or corporation known to the hospital and alleged to be liable to the injured person for the injuries received, is delivered or is mailed by registered mail, return receipt requested, postage prepaid, to each person, firm, or corporation known to the hospital and alleged to be liable to the injured person for the injuries sustained prior to the payment of any moneys to the injured person, his attorney, or legal representative as compensation for the injuries.

The hospital shall, also, deliver or mail by registered mail, return receipt requested, postage prepaid, a copy of the notice to any insurance carrier known to the hospital which has insured the person, firm, or corporation alleged to be liable to the injured person against the liability. The person, firm, or corporation alleged to be liable to the injured person shall, upon request of the hospital, disclose to the hospital the name of the insurance carrier which has insured it against the liability.