On July 1st, CA Assembly Bill 2825 was amended with key language which has upset many repair facilities in the state. They feel this will put more “work” on their plate forcing them to process even more paperwork. In my opinion, All parts and their prices should be documented. It’s only fair for all parties involved to know the true costs.

(b) The first page of the final invoice shall contain the
following statement in 12-point boldface type or larger enclosed in a
box: 
   "INSTALLING A PART, OTHER THAN A PART DESCRIBED ON THE WRITTEN
ESTIMATE, WITHOUT PRIOR APPROVAL FROM THE CUSTOMER, IS UNLAWFUL. FOR
MORE INFORMATION, PLEASE CONTACT THE STATE BUREAU OF AUTOMOTIVE
REPAIR. IF, ON THE WRITTEN ESTIMATE, YOU CHOSE TO RECEIVE COPIES OF
INVOICES FOR CRASH PARTS INSTALLED ON YOUR VEHICLE, THESE INVOICES
ARE ATTACHED TO THIS FINAL INVOICE." 
Here's a link to the most recent amendment.