You must file an appeal petition with the Yakima County Board of Equalization by July 1 of the assessment year or within 60 days of when the change of value notice was mailed, whichever date is later. Appeal forms are physically available from the clerk of the Board or the Assessor's Office. You can also find the forms online here. More information is available on the Board of Equalization Website about appealing your value. Valuation page.