King County Property Tax Appeal: The 60-Day Deadline, Comps, and a DIY Evidence Packet

King County revalues your house every single year, whether you sell it or not. When the value on the notice looks high, you get one shot to push back — and the shot has a clock on it. You have 60 days from the date printed on your own notice, or July 1, whichever is later. Most people miss it because they assume July 1 is the only deadline and file late. The people who do file on time win a reduction about a quarter of the time.

I spent years on Seattle job sites watching the Assessor's people walk the block with clipboards and a laser. The process is more mechanical than people think, and that cuts both ways: the valuation is an estimate, and an estimate can be argued. You just have to argue the one thing the Board is allowed to hear.

The deadline that actually matters

State law gives every county the same skeleton. Under RCW 84.40.038, a petition must be filed by July 1 of the assessment year, or within 30 days of the notice being mailed — or within a longer window of up to 60 days if the county adopts one. King County adopted the 60-day window. The Board of Appeals and Equalization puts it in plain language: file online or postmark the petition by July 1 of the assessment year, or within 60 days of the mailing date printed on your valuation notice, whichever is later.

The part that trips people up is the timing of the notices themselves. The Assessor's office mails valuation change notices between May and November of the assessment year. A notice mailed in June gives you until early August. A notice mailed in October gives you into December. July 1 is only the deadline for the people whose notices went out early in the spring.

The clean way to get your own date is to look it up. King County's eAppeals lookup shows the filing due date for your specific parcel. It beats guessing off a calendar.

A notice mailed in June gives you into early August. One mailed in October gives you into December. The deadline is always measured from your notice, which is why the look-up beats the calendar.

Source: RCW 84.40.038 and the King County Board of Appeals & Equalization filing-deadline guidance.

What the Board is allowed to consider

Here is the part people get wrong. The Board is not there to hear that your taxes went up too much, or that the increase is unfair, or that you cannot afford the bill. None of that moves the needle, and the County's own guidance says as much: assessment comparisons of other properties, percentage increases, personal hardship, and the amount of tax cannot be considered, citing WAC 458-14-056(5).

The only question on the table is whether the Assessor's number reflects the true and fair market value of your property. By law the Assessor is presumed correct, and the burden of proof is yours.

The evidence that wins

King County spells out the evidence that works. Comparable sales and sales of your own property come first. Then contractor estimates for repairs or defects, letters from agencies or experts about development limits, deeds showing easements that hurt value, independent appraisals, and photographs of conditions that drag the property down.

What makes a comp useful is not that it looks like your house from the street. It is that it sold close to the valuation date, in your neighborhood, with similar land and improvements. The Assessor's own appraisers use the same sales-comparison method — King County's residential valuation page says they compare your property to sales of comparable properties and, for newer structures, run a cost approach as a check. Your job is to show the sales data lands below the assessed number.

Building your own comp set

You do not need a real estate license to pull the raw material. The Assessor's eReal Property search shows every recorded sale on your parcel and, with a little clicking, the sale history of the houses around you. That is where the equity argument comes from: your most recent purchase price and the sale prices of nearby, similar houses, set against the value the Assessor assigned. The same record carries more than sales — our guide to reading a Seattle house's paper trail walks the rest of it, including the permit history behind the value.

Pull three to five sales that match on the things the Board weights — finished square footage, bedrooms and baths, year built, and location. A 1940s bungalow in Wallingford does not comp against a 2015 townhouse in Queen Anne, and a house in Magnolia carries a different land component than the same shell in Ballard. Land value is a big slice of the total in Seattle, and it varies hard by neighborhood — the neighborhood profiles measure lot size, slope, and canopy, the same things an appraiser adjusts for.

Then run the dollar math. Seattle's standard parcel carries levy code 0010, at $9.90845 per $1,000 of assessed value in 2026. Every $100,000 you knock off the assessment is about $991 back in your pocket that year — and the reduction usually sticks for more than one cycle, so the payoff compounds. That $9.90845 figure is the Seattle-standard code 0010 rate; your own parcel's levy code can differ, and the customized feasibility report applies your parcel's own code rather than the citywide default.

The tax scales in a straight line with value, and a reduction usually carries into following years. A $100,000 cut is worth about $991 in the first year — more if the lower value holds on the next roll.

Source: computed from the King County consolidated levy rate for Seattle code 0010 ($9.90845 per $1,000, 2026).

The evidence packet, line by line

The petition form itself is a checklist, and the Board cannot consider an incomplete one. Each parcel gets its own petition, and every one must carry:

1. Assessor's parcel number

   Your parcel number is on the notice and on your eReal Property record.

2. Taxpayer name, address, and representative if any

   If someone files for you, the Board needs a power of attorney on file.

3. Property description

   Address, parcel size, zoning, and basic building information — all of it on your Assessor record.

4. Value as listed by the Assessor, and your opinion of value

   Two numbers. The second one is your number, backed by the comps.

5. Specific reasons, in writing

   The petition must tell the Board and the Assessor why the determination is wrong. Market value, not hardship.

6. Signature, date, and a copy of the notice

   Attach the revaluation change notice or other determination notice.

That packet is the whole job. The parts that take real time are pulling the comps and drafting the reasons — the exact two things that decide whether the Board reads your file as a market-value argument or a complaint. If you would rather have the packet assembled for you from your own parcel's record, the Property Tax Appeal Kit pulls your sale history, levy code, and parcel details and drafts the petition text you file free through eAppeals.

DIY vs. paying a cut

There is a whole industry that will file this for you, and it charges on contingency. Ownwell, the best-known, takes nothing up front and bills a percentage of your actual savings — their pricing page walks a 25% example where a $1,000 tax reduction means a $250 fee. Their average customer who earns a reduction saves about $774 a year. That is real money, and for a lot of people the hands-off service is worth the cut.

The trade is simple. The full-service route costs a quarter to a third of whatever you save. The DIY route costs you an afternoon of pulling records — or $79 for the kit that does the pulling — and you keep every dollar. The filing itself is free either way through eAppeals, and the County's Tax Advisor office (206-477-1060 for residential) will help you sort the paperwork for nothing.

One warning worth repeating, because the County repeats it too: an appeal can occasionally move a value up, not down, in Washington. Ownwell's own page flags that they review the market data before filing and will tell you not to file if they see risk. Pull your own comps before you file, so you go in knowing the number you are arguing for is the defensible one.

And if the value on your notice jumped because the Assessor finally picked up a finished backyard cottage, the appeal is the second thing to check — the first is whether that new value is even right. Our guide to DADU property tax covers when King County books a new cottage and what it does to the roll. The customized feasibility report measures your parcel's own levy code and the build that drives the next assessment. The free homeowner checklist starts from the lot side if you are still deciding whether to build anything at all, a pre-approved standard plan keeps a simple build simple, and the Seattle DADU Pro Guide walks the whole sequence for free. If you want the Assessor's own record in front of you before you argue with it — the year built, the finished area, the full tax roll the Assessor publishes for your parcel, every recorded sale and every permit — that is the Seattle property records dossier.

Frequently asked questions

This article is educational and preliminary. It is not legal advice, tax advice, or appraisal advice. We are not licensed appraisers, tax advisers, or attorneys, and the Board of Appeals and Equalization is independent of this site. The Property Tax Appeal Kit is a self-service evidence packet and draft petition — not a guarantee of a reduction. Deadlines, levy rates, and Board procedures can change; verify everything against current King County and RCW text before you file.