Free King County guide
King County property tax appeal deadlines for 2026
Match King County's official 2026 notice mailing dates to their appeal deadlines, including the October holiday adjustment.
Look up the official due date
King County's Board of Appeals and Equalization page lets you enter a property address or parcel number to find the appeal filing due date recorded for that property.
Open King County's due-date lookupHow the 2026 dates are calculated
King County states that a valuation petition is due by July 1 of the assessment year or within 60 calendar days after the value notice is mailed, whichever is later. For the published 2026 batches below, the 60-day date is later.
Confirm the parcel before filing
The table covers the mailing batches published on King County's 2026 residential schedule. A replacement notice or a parcel record outside those batches can carry a different date, so confirm the deadline shown in eAppeals.
2026 mailing dates and appeal deadlines
These dates pair the Assessor's published residential mailing schedule with the filing rule in WAC 458-14-056.
| Notice mailed | Appeal deadline |
|---|---|
| June 18, 2026 | August 17, 2026 |
| July 16, 2026 | September 14, 2026 |
| July 23, 2026 | September 21, 2026 |
| July 30, 2026 | September 28, 2026 |
| August 6, 2026 | October 5, 2026 |
| August 13, 2026 | October 13, 2026* |
* The August 13 batch reaches 60 days on the October 12 King County holiday. The filing deadline moves to the next business day, October 13.
What to do before the date arrives
- 1.Save the notice and verify the parcel number, assessment year, and mailing date.
- 2.Check the county property record for material fact errors.
- 3.Compare the assessed value with relevant arm's-length sales near the valuation date.
- 4.State one requested value and connect every exhibit to that value.