Whether or not you contact the Assessor's office first, you have the right to file an Application for Reduced Assessment. This leads to a hearing before the Assessment Appeals Board. The Appeals Board will then determine the value based on the evidence presented by both sides.
To request an Application for Reduced Assessment, call (209) 385-7366 or write the Assessment Appeals Board at:
2222 M St.
Merced, CA 95340
Applications can also be found online under the Board of Supervisors Department, Assessment Appeals Board, Application for Changed Assessment.