California Code, Revenue and Taxation Code - RTC § 80

(1) The base-year value determined by a local board of equalization or by the State Board of Equalization, originally or on remand by a court, or by a court shall be conclusively presumed to be the base-year value for any 1975 assessment which was appealed.

(2) The base-year value determined pursuant to paragraph (1) of subdivision (a) of Section 110.1 shall be conclusively presumed to be the base-year value unless an equalization application is filed no later than the regular filing period following the 1980 lien date. Once an application is filed, the base-year value determined pursuant to that application shall be conclusively presumed to be the base-year value for that assessment.

(3) The base-year value determined pursuant to paragraph (2) of subdivision (a) of Section 110.1 shall be conclusively presumed to be the base-year value, unless an application for equalization is filed during the regular equalization period for the year in which the assessment is placed on the assessment roll or in any of the three succeeding years. Once an application is filed, the base-year value determined pursuant to that application shall be conclusively presumed to be the base-year value for that assessment.

(4) The base-year value determined pursuant to Section 51.5 shall be conclusively presumed to be the base-year value unless an application for equalization is filed during the appropriate equalization period for the year in which the error is corrected or in any of the three succeeding years. Once an application is filed, the base-year value determined pursuant to that application shall be conclusively presumed to be the base-year value for that assessment.

(5) Any reduction in assessment made as the result of an appeal under this section shall apply for the assessment year in which the appeal is taken and prospectively thereafter.