(1) The assessor must make a correction to the assessment roll for the current assessment year when the correction involves an error in the determination of the valuation of property and the following conditions are met:

(a) The assessment roll has previously been certified in accordance with RCW 84.40.320;

(b) The taxpayer has timely filed a completed petition with the board for the current assessment year;

(c) The board has not yet held a hearing on the merits of the taxpayer's petition; and

(d) The assessor and taxpayer have signed an agreement as to the true and fair value of the taxpayer's property in which agreement the parties set forth the valuation information which was used to establish the true and fair value. The true and fair value must be the value as of January 1 of the year in which the property was last revalued by the assessor.

(2) The assessor must immediately notify the board of any corrections to the assessment roll made in accordance with subsection (1) of this rule, with a copy of the notification provided to the taxpayer, and the taxpayer's petition shall be deemed withdrawn as of the date of notification to the board.