California Code, Vehicle Code - VEH § 40309

Whenever a notice of parking violation is issued in accordance withSections 40202 and 40203, or a notice of delinquent parking violation is issued pursuant to Section 40206, the amount fixed as a parking penalty for the violation charged may be forwarded by United States mail to the person authorized to receive a deposit of the parking penalty.  Payment of a parking penalty forwarded by mail is effective only when actually received, and the presumption that a letter duly directed and mailed was received does not apply.  Section 40512is applicable to a parking penalty posted pursuant to this section.