The King County 2026 property tax appeal deadline is July 1 or 60 days from your Official Property Value Notice mail date, whichever is later.
King County property tax appeals for 2026 must be filed with the King County Board of Equalization by July 1, 2026, or within 60 days of your Official Property Value Notice mail date, whichever is later. Most homeowners use the 60-day rolling rule.
Why does King County have two deadlines instead of one?
The King County Assessor mails Official Property Value Notices on a staggered schedule between May and November, so a single fixed date would leave owners who receive late notices no time to respond. State law lets you file by July 1 of the assessment year or within 60 days of the notice mail date, whichever comes later.
For a notice mailed September 15, 2026, the 60-day window closes November 14, 2026. The date printed on your notice is the one that matters, not the date it arrived in your mailbox.
What should you do with the deadline?
Pull your value notice and find the mail date in the upper corner. Add 60 days, then compare that to July 1, 2026, and use whichever is later. If you would rather not track this yourself, Fair Appeal handles the full King County property tax appeal filing and only charges 25% of first-year savings when the appeal wins. For the full process, see our King County property tax appeal guide.