A King County owner who believes the 2026 assessed value exceeds true and fair market value may petition the independent Board of Appeals and Equalization. The deadline is parcel-specific: the later of July 1, 2026 or 60 calendar days after the mailing date on the Official Property Value Notice or other determination. Because the Assessor mails notices between May and November, some valid windows remain open after July 1. File online through eAppeals or use the Board's mail or delivery instructions; email is not accepted as a petition. The Board reviews market value, not hardship, tax amount, or the percentage increase. FairPath can organize official parcel facts and owner-selected evidence, while the owner states an opinion of value, signs, files, and presents the case.
Assessment context: King County's assessment year precedes the year taxes are payable, so label the 2026 assessment separately from the 2027 tax bill it supports. Review eReal Property for parcel number, neighborhood or area, land and improvement value, lot, zoning, building area, age, grade, condition, view, waterfront or access attributes, sales history, and the notice mailing date. King County stretches from dense Seattle neighborhoods and Eastside employment centers through suburban cities, shoreline and lake markets, rural acreage, farms, and Cascade foothill parcels. School district or city alone does not establish comparability. View, topography, critical areas, easements, development restrictions, transit access, lot utility, remodeling, and micro-neighborhood can create substantial differences. Contacting the Assessor to correct a property characteristic may resolve an error, but it does not extend the Board deadline unless the official rules say so.
Filing process: A complete King County petition includes the Assessor's parcel number, taxpayer identity and address, representative and power of attorney if applicable, property description, assessed value, owner's opinion of value, and specific reasons and evidence showing the assessment is wrong. Attach the revaluation change notice or other determination. One petition is required for each parcel. eAppeals permits filing, status tracking, updates, and access to Board and Assessor documents; the county says an email confirmation should arrive within 24 hours. A paper petition may be mailed to the Board at 516 Third Avenue, Room 1222, Seattle, or hand-delivered under current instructions. Preserve the submission confirmation or postmark and the acknowledgment letter. The Board can reject an incomplete petition. Taxes remain due while an appeal is pending, and late payment can generate interest or penalties.
Evidence to review: King County presumes the Assessor's value is correct, so the owner needs market-based evidence that the value exceeds true and fair market value. The county identifies subject-property sales, comparable sales, easements, development limitations, environmentally sensitive areas, and professional estimates for maintenance issues as useful evidence. Select sales closest to the valuation date from the same competitive market and explain superior and inferior features such as location, site, view, water influence, area, age, quality, remodel, condition, parking, and restrictions. Assessment comparisons, percentage increases, hardship, and tax amount are not market-value proof. Include evidence with the petition when possible; both sides' exhibits are due 21 business days before the hearing, and late material may be excluded or cause postponement. An indexed table, source copies, dated photographs, maps, estimates, and concise adjustment explanations make the record reviewable.
Current deadline guidance: Later of July 1, 2026 or 60 days after the value-notice mailing date. A 2026 King County real-property petition must be filed online or postmarked by the later of July 1, 2026 or 60 calendar days after the mailing date printed on the Official Property Value Notice or other determination. Owners should wait for the notice and confirm the parcel-specific due date in eAppeals. Email is not a filing method.
King mails valuation change notices from May through November, so the 60-day branch can produce a parcel deadline later than the July 1 baseline.
King's eAppeals system shows the filing due date by address or parcel and lets owners track the petition and Board documents after submission.
The county lists easements, development limitations, and environmentally sensitive areas as potentially relevant evidence, important for constrained shoreline, steep-slope, and rural parcels.
Evidence from both sides is due 21 business days before the hearing; King generally gives about 45 days' hearing notice and allocates 40 minutes per appeal.
Official filing authority: King County Board of Appeals and Equalization. https://blue.kingcounty.gov/Assessor/eAppeals/
Source: King County Assessor, How to Appeal Your Valuation, https://kingcounty.gov/en/dept/assessor/buildings-and-property/property-value-and-information/appealing-a-valuation/how-to-appeal-your-valuation. Reviewed 2026-07-16.
Source: King County Board of Appeals and Equalization, How to Appeal a Property Tax Assessment, https://kingcounty.gov/en/independents/governance-and-leadership/government-oversight/board-appeals-equalization/appeal-property-tax. Reviewed 2026-07-16.
Source: King County Assessor, File Your Appeal Online, https://kingcounty.gov/en/dept/assessor/buildings-and-property/property-value-and-information/appealing-a-valuation/file-appeal-online. Reviewed 2026-07-16.
Source: King County Assessor, 2026 Property Taxes and Calendar, https://kingcounty.gov/en/dept/assessor/buildings-and-property/property-taxes/property-tax-overview/2026-taxes. Reviewed 2026-07-16.