How do I appeal my King County property tax assessment?

What the Assessor’s value is supposed to measure

Each year the King County Assessor sets a value for every parcel in the county. It’s meant to be the full market value of the property as of January 1 of the assessment year. The tax based on that value is paid the following year.

So the value notice, which the Assessor mails sometime between May and November, describes the market as it stood months earlier. That date governs every piece of evidence you gather.

With that many parcels, the Assessor works by mass appraisal: models built from recent sales, the characteristics on file for each property, and physical inspections on a rotating schedule by area. The method does well with ordinary houses on ordinary streets. It does less well with houses that differ from their neighbors. A house with a failing foundation, a view the file credits that trees now block, an awkward lot, or a front door on a busy arterial can end up valued as if it were the typical house next door.

Check your property record for errors first

Look up your parcel on the Assessor’s website and read the property detail page slowly. It lists what the county believes about your home, and a mistake there flows straight into the value. Check:

• Living area, and whether the basement is recorded as finished or unfinished
• Bedrooms, bathrooms and the year built or renovated
• The building grade and condition ratings the county assigns
• View and waterfront notes, and any noted nuisance such as traffic noise
• Garage, carport, lot size and any outbuildings

Mistakes happen. A remodel may be credited that never happened, or a view recorded that a neighbor’s addition took away years ago. If you find a factual error, contact the Assessor’s office with photos or documents. Corrections of fact can sometimes be handled directly, and the office also takes questions about values, so a call to the appraiser for your area can settle things before a formal appeal.

One caution. A conversation with the Assessor doesn’t pause the filing deadline for an appeal. If you’re not sure it will be resolved in time, file anyway.

Evidence that holds up: like-kind sales close to January 1

Under Washington law the Assessor’s value is presumed correct. To change it, you need clear, cogent and convincing evidence that it’s wrong. Your sense that the number feels high won’t meet it, and neither will the size of the increase from last year. A neighbor’s lower assessment won’t either: the Board’s own guidance says it can’t consider comparisons with other properties’ assessments, the amount of tax or personal hardship. It wants to know what your home was worth, and sales show that directly.

The strongest evidence is a set of sales of homes truly like yours. Picture a street in Bellevue’s Lake Hills: ramblers with carports next to split-levels, some original and some rebuilt inside. If you own an original rambler, the sales that matter are other ramblers of similar size and age and condition, nearby, that sold in the months around January 1. The updated split-level down the block tells the board very little about your house. A condominium should be compared with units in the same building or a very similar one. Waterfront compares with waterfront, and a view home with other view homes.

Sales well after January 1 describe a different market and carry less weight. When a comparable sale differs from your home in some way (a bigger lot or a newer kitchen, for example), say how, and show how that should move the value.

It’s the same work that goes into pricing a house for sale, which I describe on the selling page. A strong petition usually rests on some of the following:

• Several like-kind sales near January 1, with addresses, dates, prices and a short note on how each compares with your home
• Your own purchase, if you bought close to January 1 in an ordinary sale on the open market
• An appraisal from a licensed appraiser with an effective date near January 1
• Contractor bids and photos for problems that existed on January 1, such as a failing roof or foundation damage

Filing with the Board of Equalization, and the deadline on your notice

Formal appeals go to the King County Board of Equalization (formally the Board of Appeals and Equalization), which is separate from the Assessor’s office. Petitions can be filed online through the Board’s website, one petition per parcel. You’ll state the value you believe is correct and provide your evidence, either with the petition or by the Board’s evidence deadline before your hearing.

The filing deadline is printed on your value notice. Treat it as fixed. Missing it generally ends your chance to appeal that year’s value, and the Board has little room to accept late petitions.

Keep paying your property taxes on schedule while the appeal is pending. If the value is lowered, the tax is adjusted afterward.

What happens after you file

An appraiser from the Assessor’s office reviews the petition. Sometimes the Assessor proposes a revised value, and if you accept it, the appeal ends there.

If not, the Board schedules a hearing. You can take part by phone, or let the Board decide on the written materials without attending. At the hearing you present your evidence, the Assessor’s representative presents theirs, and the Board issues a written decision based on what was in front of it. The gap between filing and hearing varies from year to year and can run long.

If you disagree with the Board’s decision, you can appeal to the Washington State Board of Tax Appeals. That appeal has its own short deadline, which the decision will explain.

When an appeal won’t change your tax bill much

In Washington, the taxing districts (the county, your city, the school district, fire, library and others) each set how much property tax they collect, within limits set by state law and by voters. The total is then spread across the assessed values in each district.

That has two consequences. If values across your taxing districts rise by roughly the same proportion, your share of the levy doesn’t change much, and a big jump in your assessment doesn’t mean an equally big jump in your bill. And if you win a lower value, your tax falls by less than the value did, because the rate is set from everyone’s values together.

So an appeal pays off when your value is out of line with homes like yours. It pays off much less when the whole neighborhood’s values moved together, even if you think the whole neighborhood is overvalued.

If your aim is a smaller bill, also check the exemption programs. Washington offers property tax exemptions and deferrals for qualifying seniors, people with disabilities and disabled veterans, based on income, and for some owners that matters more than any appeal could. The Assessor’s exemptions staff can tell you if you qualify.

The assessed value also isn’t a sale price. Buyers and their appraisers work from sales, so if you’re thinking about selling in the next year or two, price from those. The comparable sales that support an appeal are where that conversation starts. And if you add to the property later, say with one of the backyard cottages or second ADUs most King County cities now permit, expect the new construction to show up in a later assessment.