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 |
|---|---|---|---|---|---|
| 0467••• | Industrial Park | $9,549,550 | $40,781,500 | 4.27× | ~$287,334/yr |
| 7666••• | Apartment(Mixed Use) | $56,331,593 | $76,623,000 | 1.36× | ~$186,681/yr |
| 3026••• | Retail(Discount) | $10,168,533 | $29,079,800 | 2.86× | ~$173,984/yr |
| 1225••• | Warehouse | $20,900,000 | $33,809,100 | 1.62× | ~$118,764/yr |
| 7666••• | Office Building | $4,959,438 | $16,691,500 | 3.37× | ~$107,935/yr |
| 1972••• | Retail Store | $1,400,000 | $7,611,900 | 5.44× | ~$57,149/yr |
| 0697••• | Parking(Commercial Lot) | $1,000,000 | $6,362,400 | 6.36× | ~$49,334/yr |
| 7681••• | Medical/Dental Office | $800,000 | $6,028,400 | 7.54× | ~$48,101/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: King appeal deadline · how to lower King taxes.