332.1.1 DEFINITIONS (PENAL CODE 14213)
Missing Person Any person whose whereabouts are unknown to the reporting party including, but not limited to, a child taken, detained, concealed, enticed away or retained by a parent in violation of Penal Code § 277. Missing person also includes any child who is missing voluntarily, involuntarily or under circumstances not conforming to his/her ordinary habits or behavior and who may be in need of assistance.

Child-

While California considers a child to be a person under eighteen years of age, for purposes of this section federal law considers any person under the age of twenty one years to be a child. 

According to 

https://www.police.ucla.edu/other/missing-persons

CLETS Missing Person System Report Types --- It is up to the officer taking the report to determine which type and category the report falls into.

(a) Voluntary Missing Adult Missing adult who has left of his/her own free will.

(b) Stranger Abduction Missing person taken by a stranger. Includes cases of a known abductor who is not a family member. If under 18, this information will be forwarded to the FBI’s Child Abduction and Serial Killer Unit (CASKU) and the National Center for Missing and Exploited Children (NCMEC).

(c) Parent/Family Abduction Missing juvenile taken by parent or nonparent family member.

(d) Runaway Missing juvenile is reported as a runaway or is not wanted by his/her parents.

(e) Suspicious Circumstances Person missing under circumstances that may indicate foul play. If under 18, this information will be forwarded to the FBI’s CASKU and the NCMEC.

(f) Catastrophe Missing person is a victim of a disaster (e.g., boating accident, plane crash, earthquake, flood, fire).

(g) Lost Missing person who has strayed away and whose whereabouts are unknown. circumstances surrounding missing person’s disappearance are unknown.

(i) Dependent Adult Missing adult (over age 18) who has physical or mental limitations, which restrict his/her ability to carry out normal activities.

Officers may use discretion when determining the presence of risk based on experience, expertise and the specific facts and circumstances of each case.

332.2 REPORT ACCEPTANCE
All personnel shall accept any report, including any telephone report, of a missing person, including runaways, without delay and shall give priority to the handling of these reports over the handling of reports relating to crimes involving property. Reports shall be taken on missing persons regardless of jurisdiction. Penal Code § 14205 (a)

https://codes.findlaw.com/ca/penal-code/pen-sect-14211.html

(d) If the missing person is under 21 years of age, or there is evidence that the person is at risk, the police department or sheriff's department shall broadcast a “Be On the Lookout” bulletin, without delay, within its jurisdiction.

(e) If the person reported missing is under 21 years of age, or if there is evidence that the person is at risk, the law enforcement agency receiving the report shall, 

within two hours after the receipt of the report, electronically transmit the report to the Department of Justice via the California Law Enforcement Telecommunications System for inclusion in the Violent Crime Information Center and the National Crime Information Center databases.

(f) Information not immediately available for electronic transmission to the department shall be obtained by the investigating agency and provided as a supplement to the original entry as soon as possible, but in no event later than 60 days after the original electronic entry.  Supplemental information may include, but is not limited to, the following:

(1) Dental records and treatment notes.

(2) Fingerprints.

(3) Photographs.

(4) Description of physical characteristics.

(5) Description of clothing the person was wearing when last seen.

(6) Vehicle information.

(7) Other information describing any person or vehicle believed to be involved in taking, abducting, or retaining the missing person.

 Department of the California Highway Patrol taking the report shall, without delay, and, in the case of persons under 21 years of age or where there was evidence that the missing person was at risk, within no more than 24 hours, notify, and forward a copy of the report to the police or sheriff's department or departments having jurisdiction of the residence address of the missing person or runaway and of the place where the person was last seen.  The report shall also be submitted by the department or division of the Department of the California Highway Patrol which took the report to the center.  The initial California Law Enforcement Telecommunications System record may only be removed after the receiving agency has accepted the report.

Legal Resources | Penal Code |  PC  14215  

Missing Persons   

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(a) As used in this title, "missing person" includes, but is not limited to, any of the following:

(1) An at-risk adult.

(2) A child who has been taken, detained, concealed, enticed away, or retained by a parent in violation of Chapter 4 (commencing with Section 277) of Title 9 of Part 1.

(3) A child who is missing voluntarily or involuntarily, or under circumstances not conforming to his or her ordinary habits or behavior and who may be in need of assistance.

(b) As used in this title, "at risk" means there is evidence of, or there are indications of, any of the following:

(1) The person missing is the victim of a crime or foul play.

(2) The person missing is in need of medical attention.

(3) The person missing has no pattern of running away or disappearing.

(4) The person missing may be the victim of parental abduction.

(5) The person missing is mentally impaired.

(c) As used in this title, "child" is any person under 18 years of age.

(d) As used in this title, "center" means the Violent Crime Information Center.

(e) As used in this title, "dental or medical records or X-rays" include all those records or X-rays which are in the possession of a dentist, physician and surgeon, or medical facility.

(f) As used in this title, "unidentified person" means a person, living or deceased, whose identity the local investigative agency is unable to determine.

(Amended and Renumbered by Stats. 2014, Ch. 437, Sec. 27.)