California Code, Revenue and Taxation Code - RTC § 744

(a) The board shall notify the petitioner of its decision on a petition for reassessment by mail and shall make written findings and conclusions if requested at or prior to the commencement of the hearing. The board shall send a periodic report of its decisions and any written findings and conclusions thereon to each county in which affected state-assessed property is situated. The findings shall fairly disclose the board's determination of material factual issues and shall contain a statement of the method or methods of valuation used by the board in valuing the property. Notwithstanding the requirement for a statement of method or methods, the board's approval of a settlement of a lawsuit contesting the value of state-assessed property shall be sufficient disclosure when value is determined in accordance with a board-approved settlement. Decisions of the board on petitions for reassessment of state-assessed property shall be completed on or before December 31.

(b) When the value of an assessee's state-assessed property is determined, after a hearing on a petition for reassessment, to be different from the value originally adopted by the board, the board shall determine the year in which the corrected value is to be entered on the roll. The correct value may be entered on the roll for the fiscal year in which the determination is made, or the difference between the original and the corrected value may be entered as an increase or decrease in the assessment for the succeeding fiscal year. If the corrected value is entered on the roll for the fiscal year in which it is determined, and the board roll has been transmitted to the county auditors, the board shall make the corresponding changes in allocations and transmit the roll corrections to the county auditor.

(c) If the amount of the correction is to be entered on the roll for the succeeding fiscal year, an amount is to be added in lieu of interest. If the correction results in a reduction in assessed value, there shall be added to the reduction, in lieu of interest, 9 percent of the difference between the original assessed value and the reduced assessed value. If the correction results in an increase in assessed value, there shall be added to the increase, in lieu of interest, 9 percent of the difference between the original assessed value and the increased assessed value.