King County Property Tax Appeal 2026
How to appeal your property assessment in King County (Seattle), WA. Everything below is pulled from King County Department of Assessments. Always confirm the current details with the county before filing — this is general information, not legal advice.
By July 1, or within 60 days of the date your Official Property Value Notice was mailed — whichever is later
$750,000
~0.9% effective rate
Taxpayer Petition to the County Board of Equalization
King County property tax appeal deadline 2026
The 2026 deadline to appeal your King County property assessment is By July 1, or within 60 days of the date your Official Property Value Notice was mailed — whichever is later. File your Taxpayer Petition to the County Board of Equalization with King County Department of Assessments on or before that date — miss it and you generally wait until next year. File as early in the window as possible to secure a hearing slot.
Who assesses & hears your appeal
King County Department of Assessments
Appeals are heard by the King County Board of Equalization.
How to file in King County
Online via the King County Board of Equalization e-Appeals portal
kingcounty.gov/depts/assessor.aspxMail the Taxpayer Petition to the Board of Equalization
516 3rd Ave, Room 1222, Seattle, WA 98104
Washington assesses at 100% of market value. King County mails value notices on a rolling area schedule, so your 60-day window depends on when your notice was issued.
King County property tax appeal FAQ
When is the King County appeal deadline?
By July 1, or within 60 days of the mailing date on your Official Property Value Notice, whichever is later.
Deadlines, forms, and contact details change — always confirm with King County Department of Assessments before filing. This is general information, not legal advice.
Appeal your King County assessment
Check your property for $4.99 (credited), then get the full comparable-sales packet and AI appeal letter for a flat $29 — $19 at launch. Built for WA filings.