You're over-assessed when the County's value is higher than what your home would actually sell for — and then you're over-paying every year until you appeal. Washington petitions to the county Board of Equalization are due July 1 of the assessment year, or within 60 days of the Assessor's value-change notice (whichever is later), per RCW §84.40.038.
Live King County parcels whose assessed market value exceeds their recent arm's-length sale price — a real over-assessment signal pulled from the public assessor roll. If your parcel looks like these, you have a strong appeal:
| PIN | Use | Recent sale | County says mkt | Over | Indic. overpay |
|---|---|---|---|---|---|
| 1991••• | Office Building | $49,032,890 | $166,844,000 | 3.4× | ~$1,083,862/yr |
| 3323••• | Hotel/Motel | $15,285,000 | $90,888,700 | 5.95× | ~$695,554/yr |
| 5223••• | Retail(Line/Strip) | $4,472,865 | $42,410,600 | 9.48× | ~$349,027/yr |
| 0653••• | Office Building | $15,750,000 | $42,870,700 | 2.72× | ~$249,510/yr |
| 1544••• | Art Gallery/Museum/Soc Srvc | $5,000,000 | $29,633,000 | 5.93× | ~$226,624/yr |
| 2771••• | Industrial(Lignt) | $5,597,660 | $27,988,300 | 5× | ~$205,994/yr |
| 1983••• | Apartment | $59,880,000 | $77,423,300 | 1.29× | ~$161,398/yr |
| 1142••• | Office Building | $26,900,000 | $44,113,000 | 1.64× | ~$158,360/yr |
Most owners who win use a contingency property-tax appeal firm — it costs nothing unless they cut your bill, then takes a share of the first-year saving. About 95% of over-assessed owners never appeal, so the saving is usually left on the table.
Open the official King County appeal page → Confirm the official deadline →against the official King County / WA deadline (kingcounty.gov · RCW §84.40.038). These are public deadline facts, not legal or tax advice — confirm your exact date with the County Board of Equalization and consult a professional before filing.
More for King County: how to lower King taxes · King property tax appeal.