California Code, Vehicle Code - VEH § 2525.6

Each fleet owner licensed as an inspection and maintenance station may place upon a vehicle which it has inspected and maintained, or upon which it has installed or adjusted required equipment, a sticker, in a form approved by the commissioner, certifying the compliance of such vehicle with all pertinent requirements imposed upon such vehicle by this code or regulations adopted thereunder and, if applicable, by the United States Department of Transportation.  Such stickers shall remain valid for a period of one year and shall not be placed on any vehicle which is not part of the fleet.