Many of the procedures and duties of the Mariposa County Assessor's Office are guided or in fact mandated by the California State Legislature or state agencies such as the California State Board of Equalization. As we have fulfilled our responsibilities to California's citizens and residents over the years, a vocabulary and set of concepts has developed to facilitate the implementation of these procedures and duties.


  1. A through E
  2. F through L
  3. M through P
  4. R through U

Agricultural Preserve

Agricultural preserve land is one of several types of enforceably restricted properties that are valued according to their productive capacity rather than their market value.

Assessment Appeal

A taxpayer may file an appeal for reduction of the annual assessed value with the Clerk, Board of Supervisors during the regular filing period each year, July 2 until September 15. For supplemental or escape assessments, appeals must be filed within 60 days of the mailing of the tax bill or receipt of the notice, whichever is earlier.

Assessor's Parcel Number (APN)

The Assessor's identification number for a specific property.

Base Year

Under Proposition 13 the assessment year 1975-76 serves as the original base year. Thereafter, any assessment year in which real property, or a portion thereof, is purchased, is newly constructed or changes ownership shall become the base year used in determining the full value for such real property, or a portion thereof.

Business and Personal Property Assessment; Assessment of Boats and Aircraft

Machinery, equipment, tools, furniture, fixtures, and leasehold improvements held or used in connection with a trade or business are taxable. In addition, most boats, aircraft and mobile homes are also taxable. Supplies on hand, demonstration equipment, and construction in-progress are also assessable.

Change of Ownership

The conveyance of an interest in real property from one person or entity to another requiring reappraisal of real property under California law.

Change of Ownership Exclusions

Some changes in ownership may be excluded from reappraisal if a timely claim is filed with the Assessor's Office that meets specific qualifications. Examples include the transfer of real property between parents and children; or the replacement of a principal residence by senior citizens over age 55 within Mariposa County.

CPI (Consumer Price Index)

The annual inflation factor is an integral part of the law established by Proposition 13. It requires that assessed values must be increased each year the same amount as the Consumer Price Index (CPI) increase for that year, up to a maximum of 2%.


A deduction from the taxable assessed value of property as prescribed by law, generally based on the property's use.