California Vehicle Code section 16000 mandates the reporting of the accident. See this link for more information:
HOWEVER, subsection (c) reads, "If none of the parties involved in an accident has reported the accident to the department under this section within one year following the date of the accident, the department is not required to file a report on the accident and the driver's license suspension requirements of Section 16004 or 16070 do not apply."
As stated above, this is an incomplete answer but an attempt to provide a cursory overview of a subject that attorneys 'practice' and improve upon during the entirety of their legal careers. This response is not meant as legal advice or as a legal opinion. Such advice would be impossible or impractical without additional information and more facts giving rise to the question. A consultation with an attorney is necessary.