King County tax assessor: how assessments, appeals, and exemptions work

Last updated 2026-07-09

What does the King County Assessor actually do?

The King County Assessor estimates the market value of every taxable parcel in the county as of January 1 each year. ^[1] That number, the assessed value, is what the county uses to calculate your property tax bill. The office does not set the tax rate and does not collect a dime. Those jobs belong to individual taxing districts and King County Treasury.

The office values roughly 700,000 parcels across 39 cities and unincorporated King County. ^[1] That makes it one of the largest assessment operations in the Pacific Northwest. Staff appraisers use mass appraisal, which means they model groups of similar properties using sales data, cost data, and income data. Nobody is walking through your living room every year.

When your assessed value spikes, the cause is almost always rising sale prices in your neighborhood. State law backs this up. RCW 84.40.030 requires the assessor to value property at 100 percent of "true and fair value in money." ^[2] That phrase has a specific legal meaning: the price a willing buyer and a willing seller would agree on in an arm's-length sale. If the assessor's number sits above that, you have a real appeal.

How does King County calculate your assessed value?

The assessor uses three standard approaches depending on the property: sales comparison, cost, and income. For single-family homes, sales comparison does most of the work. Appraisers pull recent sales of similar homes in your neighborhood, adjust for differences in size, age, condition, and features, then land on a value for your house. ^[3]

The cost approach carries the load for new construction and odd properties where comparable sales are thin. It estimates what it would cost to rebuild the structure today, subtracts depreciation for age and wear, and adds land value. The income approach applies mostly to commercial and rental property, using capitalized net operating income.

King County reappraises physically on a six-year cycle by neighborhood, with market updates every year in between. ^[1] Your full inspection may happen once every six years. Your value gets refreshed annually based on where the market moved. That gap is why your assessment can jump hard even though nothing about your house changed. The market moved, and the model caught it.

Here is the detail people miss. The value on your notice is the taxable value for next year's bill, not this year's. The value set January 1, 2025 generates the 2026 tax bill. Keep that lag straight when you compare your assessed value to what homes are actually selling for right now.

When does King County send assessment notices, and what is the appeal deadline?

King County mails value change notices on a rolling basis, generally February through August, depending on which neighborhood cycle is up for review. ^[1] You do not get a notice every year. You get one when your value changed or when your area hits its revaluation year.

The appeal deadline is 60 days from the date printed on your notice, not the date you opened the envelope. ^[4] This is the single most important number in the process. Miss it and you lose your right to appeal that assessment year. There is no hardship extension in most cases.

Event	Timing
Assessment date (lien date)	January 1
Value notices mailed	February through August (varies by area)
Appeal deadline	60 days from notice date
Board of Equalization hearings	Typically 6-18 months after filing
Tax bill mailed	February of the year after assessment
First-half tax due	April 30
Second-half tax due	October 31

Didn't get a notice but suspect your value changed? Check the assessor's eReal Property portal. ^[1] Your clock may already be running. The portal shows the notice date on record, and the 60-day window starts from that date whether or not the mail reached you.

Other large western counties run on different calendars entirely. Lane County, Oregon, for example, follows Oregon law with a September 25 certification deadline and a January 2 through April 1 appeal window, a structure that looks nothing like King County's rolling notices. ^[5] Own property in both states? Do not assume the rules carry over.

How do you appeal a King County property tax assessment?

Appeals go to the King County Board of Equalization (BOE), an independent quasi-judicial body separate from the Assessor's Office. ^[4] You file a petition, the BOE sets a hearing, and you present your evidence. The assessor defends its value. A three-member panel decides.

Step one: gather evidence before you file. Pull your property record from the eReal Property portal and hunt for errors: wrong square footage, wrong bedroom or bathroom count, wrong lot size, a condition rating that does not match your house. Errors are free wins. No errors? Then you need comparable sales.

Step two: find recent sales of genuinely similar homes within about half a mile and within six months of January 1 of the assessment year. Use the King County residential sales lookup or a public MLS search. Match on square footage (within 15 to 20 percent), age, condition, and lot size. Three to five solid comps beat a dozen weak ones. More is not better when the extras are junk.

Step three: file the BOE petition. You can file online through the BOE's portal or mail a paper form. The filing fee for residential property owners is $0. ^[4] Attach your comps or submit them before your hearing deadline.

Step four: show up for your hearing. BOE hearings run short, usually 15 to 30 minutes. State your case calmly. Present your comps. Explain your adjustments. You do not need to be a licensed appraiser to walk through this. The panel asks questions, and you get a written decision, usually within a few weeks.

Lose at the BOE? You can escalate to the Washington State Board of Tax Appeals or Superior Court. ^[2] Most homeowners stop at the BOE because the cost of going further rarely pencils out on a residential property unless the gap is large.

A good DIY appeal kit (like the one at TaxFightBack) walks you through building the comp package and finishing the BOE petition, so you keep the savings instead of handing 30 to 40 percent to a contingency firm.

What evidence actually wins a King County BOE hearing?

The BOE's standard is plain: your evidence has to show the assessor's value exceeds true and fair market value as of January 1. ^[4] Everything you bring should point at that date.

Sales comparables win residential cases. A sale of your own home near the assessment date is the strongest single data point there is. Your house sold in October for $580,000 and the assessor set January 1 value at $650,000? That sale is nearly impossible to argue against.

For homes that haven't sold, bring three to five arm's-length sales of similar properties, all within about six months of January 1. Skip foreclosures, estate sales, and related-party deals. The assessor will argue those are not arm's-length, and the panel usually agrees. Stick to MLS or county sales records.

An independent appraisal is legitimate evidence, but weigh the cost first. A licensed residential appraisal in King County runs about $500 to $900. ^[6] If your assessment is $50,000 too high and your effective rate is roughly 1 percent, your annual overcharge is about $500. The appraisal pays for itself in year one if you win. Spend the money only when you are confident you will win, or when the comps are ambiguous and the dollars are big.

Photos of deferred maintenance, foundation trouble, a failing roof, or other physical problems support a lower condition rating. The assessor grades condition as very good, good, average, fair, or poor. Even one step down can move your value a real amount.

What does not work: arguing your taxes are too high, that you are on a fixed income, or that your neighbor's assessment looks low. The BOE hears evidence about market value and nothing else. Everything else is noise to them.

What exemptions and programs can reduce your King County property tax bill?

King County runs several programs that cut or freeze your assessed value or your bill directly. These are separate from the appeal process, and you should check them before you decide whether to appeal.

The Senior Citizen and Disabled Persons Property Tax Exemption is the big one. ^[7] Under RCW 84.36.381, qualifying homeowners get a reduction in assessed value and a cap on their tax. To qualify for 2025, you must be 61 or older (or disabled), own and occupy the home as your primary residence, and have combined household disposable income at or below $84,000. That $84,000 figure is the 2025 threshold. The benefit comes in three income tiers:

Income tier	Benefit
$0 to $42,000	Exempt from excess levies; value frozen at base year amount
$42,001 to $55,000	Exempt from excess levies; value reduced by 35%
$55,001 to $84,000	Exempt from excess levies only

You apply directly with the King County Assessor. The deadline is December 31 of the year before you want the benefit to start, though the office sometimes takes late applications for good cause.

The Home Improvement Exemption lets you add up to $60,000 in value through certain improvements without that value being taxed for up to three years. ^[7] It covers improvements for the disabled, added living quarters for a family member, and code-required work on older homes.

The Open Space, Farm and Agricultural, and Timber Land current-use programs cut assessed value for qualifying land by taxing it at its current use instead of its highest and best use. ^[8] These matter most for rural parcels at the edge of the county.

Veterans and active military may qualify for extra relief depending on disability rating. The Washington State Department of Revenue keeps the official eligibility summaries for these programs. ^[9]

How do you look up your King County property assessment online?

The King County Assessor's eReal Property portal is the main public lookup tool. ^[1] Go to the assessor's website at kingcounty.gov/depts/assessor and click into eReal Property. Search by address, parcel number, or owner name.

Once you find your parcel, you see the assessed value split between land and improvements (the structure). You also see the assessment history going back years, the physical characteristics on file (square footage, year built, bedrooms, condition), and recent area sales. Open the property detail page and read every field. Any factual error is grounds for an appeal or a correction request that may not even need a formal hearing.

The portal also shows the comparable sales the assessor used to value your property, which is worth its weight in gold. If the assessor's own comps come in below the assessed number, you have an argument on day one. If the comps are genuinely similar and support the value, you now know your case is harder.

For tax bills and payment history, go to King County Treasury, not the assessor. The Treasury site is at kingcounty.gov/depts/finance/treasury and shows your current and prior bills, payment status, and levy breakdowns by taxing district.

How does King County property tax compare to other large counties?

King County's effective property tax rate has historically run between 0.8 and 1.1 percent of assessed value for a median single-family home, though the exact rate swings by city and taxing district. ^[10] Bellevue, Seattle, and unincorporated areas all carry different levy combinations.

Washington has no personal income tax, so property and sales taxes carry a heavier load than in states that spread revenue across three sources. The state constitution, Article VII, caps the total combined regular levy at $10 per $1,000 of assessed value, and the legislature has capped state and local regular levies together at $5.90 per $1,000. ^[11] Voter-approved excess levies, which fund schools heavily in King County, sit on top of that.

Lane County, Oregon comes up constantly in Pacific Northwest property tax searches because it covers a large, mixed county including Eugene. It runs on a different framework. Oregon's Measure 5 caps education levies at $5 per $1,000 of real market value and non-education levies at $10 per $1,000, and Measure 50 limits assessed value growth to 3 percent per year regardless of what the market does. ^[5] Oregon owners tend to have steadier bills year to year. The tradeoff is that their assessed value can drift far below true market value over time, which means a big tax jump when the property finally sells.

Want to see how appeal-heavy other big metro counties are? Los Angeles, Cook County (Illinois), and Maricopa County (Arizona) all run formal appeal processes with different timelines and evidence standards. See our guides on los angeles county property tax, cook county tax assessor tax bill, and maricopa property tax for side-by-side context.

What happens after you file a King County BOE appeal?

Once you file, the BOE sends the assessor a copy of your petition. The assessor builds a hearing package with its evidence and sends it to the BOE and to you before the hearing. Read that package closely. If the assessor's own submission has errors or weak comps, flag them by name.

Hearing waits have run from six months to well over a year depending on the volume of appeals that year. You do not pay a different amount while the appeal is pending. Your original bill is still due on the normal schedule (April 30 and October 31), and you should pay it on time to dodge interest. If you win, the county issues a refund or credits your next bill. ^[12]

The BOE mails you a written decision. If they agree with you fully, the assessor corrects the record and the next tax cycle reflects the new value. If they split the difference, you get partial relief. If they uphold the assessor, you can appeal to the Washington State Board of Tax Appeals within 30 days. ^[9]

One thing to know: a win this year does not lock in your value for future years. The assessor can raise it again in later cycles. Plenty of homeowners who win are startled to see a big jump two years later. The fix is simple. Watch your notice every year and appeal again when the evidence supports it. For a closer look at what happens once the decision is final, see our guide on after-the-appeal.

Counties like san diego property tax and lake county property tax have their own post-appeal steps worth knowing if you own property in more than one place.

How do you contact the King County Assessor's Office?

The King County Assessor's main office is at 500 Fourth Avenue, Suite 700, Seattle, WA 98104. ^[1] The phone number is 206-296-7300. Hours run Monday through Friday, 8:30 a.m. to 4:30 p.m.

For most assessment questions, the fastest route is the eReal Property portal or the assessor's online contact form. For exemptions, download the form from the assessor's website and mail it or bring it in person. For BOE petitions, the board has its own office at 516 Third Avenue, Room 1222, Seattle, WA 98104, and its own line at 206-477-3400. ^[4]

Do not confuse the Assessor with the Treasurer (tax payments), the Recorder (deed recording), or the BOE (appeals). They are separate offices. Calling the wrong one burns time you may not have if your deadline is close.

Working with a tax agent or attorney? They can file a Notice of Representation with the BOE for you. For a typical residential appeal, though, you can represent yourself with no procedural hurdle. The BOE is built to be usable by property owners without legal training.

Should you hire a property tax consultant or appeal yourself?

The math here is usually simple. Contingency firms in the Seattle market typically charge 25 to 40 percent of your first year's tax savings. ^[6] If your appeal saves $800 a year, the firm keeps $200 to $320. You keep $480 to $600. Do it yourself and you keep all $800.

A consultant earns their fee when the property is commercial or income-producing and needs an income approach, when the assessed value is very high and the savings justify professional-grade evidence, or when the case is headed to Superior Court and you actually need a lawyer.

For a typical single-family home where the problem is bad comps or a factual error, DIY works. The BOE hears from unrepresented homeowners all day. The forms are plain language. Staff can answer procedural questions, though they will not build your strategy for you.

TaxFightBack's DIY appeal kit hands you the comp analysis framework and a petition walkthrough in plain steps, so you keep 100 percent of your savings. If your situation is genuinely complicated (commercial property, income approach required, past appeals that went nowhere), a professional fee may be money well spent.

Curious how DIY plays out in other high-value markets? See our guides on bexar county tax assessor and gwinnett county tax assessor for county-specific tips homeowners have used without hiring a firm.

What are common mistakes King County homeowners make when appealing?

Missing the 60-day deadline is the most common and most expensive mistake. People get the notice, figure they have time, and then find out they are past the cutoff. Set a calendar alert the day the notice lands.

Using the wrong comparable sales is second. Distressed sales, related-party sales, and sales too far from your property or too far from January 1 all get discounted by the assessor or the BOE. Stick to arm's-length MLS sales within six months and half a mile when you can.

Arguing fairness instead of value is a classic. The BOE cannot lower your value because your taxes feel unfair or because your neighbor pays less. They act only on evidence that the assessed value exceeds true and fair market value.

Skipping the property record review leaves money on the table. Roughly 10 to 15 percent of properties carry at least one factual error, based on assessor audits around the country (no precise King County figure is published, so treat that range as a rough national benchmark). Check every field: square footage, year built, bath count, condition grade. A phantom bathroom or 200 extra square feet of living space can add tens of thousands to your assessed value.

Waiting for the tax bill to appeal does not work. The deadline runs from the assessment notice, not the bill. By the time the February tax bill shows up, your window for that year's value may already be shut.

Frequently asked questions

What is the King County Assessor's Office phone number and address?

The King County Assessor's Office is at 500 Fourth Avenue, Suite 700, Seattle, WA 98104. The phone number is 206-296-7300. Office hours run Monday through Friday, 8:30 a.m. to 4:30 p.m. For appeals, contact the separate King County Board of Equalization at 516 Third Avenue, Room 1222, Seattle, or call 206-477-3400.

How long do I have to appeal my King County assessment?

You have exactly 60 days from the date printed on your assessment notice to file a petition with the King County Board of Equalization. This deadline is firm. It runs from the notice date, not the date you received it or the date of the tax bill. Miss it and you forfeit your right to appeal for that year.

What income limit applies to the King County senior property tax exemption?

For 2025, combined household disposable income must be $84,000 or below. You must also be 61 or older (or disabled) and own and occupy the home as your primary residence. The benefit comes in three tiers by income, with the lowest tier providing both a value freeze and exemption from excess levies.

Does King County reassess every year?

King County updates assessed values annually, but full physical reappraisals happen on a six-year neighborhood cycle. Each year, values shift using market trend data even without a physical inspection. So your value can change every year. You receive a notice only when your value changes or when your neighborhood hits a full revaluation year.

Can I appeal a King County assessment without a lawyer or tax agent?

Yes. The King County Board of Equalization is built to be usable by homeowners without professional representation. You file a petition, submit comparable sales or other market evidence, and present your case at a short hearing. No legal training is required. Many homeowners cut their assessments by representing themselves with solid sales comparables.

What is the King County property tax due date?

King County property taxes are due in two installments. The first half is due April 30 and the second half is due October 31. If you pay the full amount by April 30, no second payment is required. Payments postmarked after the due date accrue interest at 1 percent per month plus a 3 percent penalty.

Where can I find my King County assessed value online?

Use the King County Assessor's eReal Property portal at kingcounty.gov/depts/assessor. Search by address, parcel number, or owner name. The portal shows assessed value, property characteristics, assessment history, and recent area sales. For tax bills and payment history, use the King County Treasury site at kingcounty.gov/depts/finance/treasury.

What is the King County effective property tax rate?

The effective rate varies by city and taxing district but has historically run between roughly 0.8 and 1.1 percent of assessed value for a median single-family home. Seattle, Bellevue, and unincorporated areas all carry different levy combinations. Voter-approved excess levies, especially for schools, drive much of the variation across the county.

What evidence does the King County Board of Equalization accept?

The BOE accepts recent arm's-length sales of comparable properties, independent fee appraisals, photographs documenting condition issues, and documentation of factual errors in your property record. The standard is evidence that your assessed value exceeds true and fair market value as of January 1 of the assessment year. Fairness arguments or comparisons to neighbors' tax bills carry no weight.

How is King County's appeal process different from Lane County, Oregon?

King County (Washington) requires a petition to its Board of Equalization within 60 days of your notice. Lane County, Oregon runs under Oregon law with a different calendar: certification happens September 25, and appeals go to the Oregon Magistrate Division with a January 2 through April 1 window. Oregon's Measure 50 also caps annual assessed value growth at 3 percent, giving owners steadier baselines than Washington's market-value system.

If I win my King County appeal, do I get a refund?

Yes. If the BOE reduces your assessed value and you already paid taxes based on the higher number, the county issues a refund or credits your next bill. Pay your original bill on time while the appeal is pending to avoid penalties and interest. The correction flows through after the decision is final.

What is the King County Board of Equalization filing fee?

There is no filing fee for residential property owners appealing to the King County Board of Equalization. The process is free to start. You cover your own costs for any evidence you gather, such as a professional appraisal, but there is no charge simply to file the petition and request a hearing.

Can new construction be appealed in King County?

Yes. New construction gets an initial assessed value when the building permit closes out, and the owner receives a notice with the standard 60-day appeal window. New construction values often come from cost-approach modeling rather than comparable sales, so factual errors in square footage or grade are common and worth checking on the property record before the deadline.

How does the King County Assessor determine land value separately from the house?

The assessor values land by analyzing sales of vacant lots and pulling land-residual figures from improved-property sales in each neighborhood. Land value and improvement value show up as separate line items on your notice and in eReal Property. You can appeal either one. Land-only appeals are less common but viable when comparable vacant land sales support a lower value.

Sources

1. King County Assessor's Office - official homepage and eReal Property portal: The King County Assessor values roughly 700,000 parcels on a six-year neighborhood cycle with annual market-trend updates, using eReal Property as the public lookup portal.
2. Washington State Legislature - RCW 84.40.030, True and fair value requirement: Washington law requires property to be valued at 100 percent of true and fair value in money, meaning the price a willing buyer and seller would agree on at arm's length.
3. Washington State Department of Revenue - Property Tax division, appraisal methods: Washington assessors use the sales comparison, cost, and income approaches to value property, with sales comparison dominant for residential parcels.
4. Oregon Department of Revenue - Property Tax, Measures 5 and 50 overview: Oregon's Measure 50 caps assessed value growth at 3 percent per year; Measure 5 caps education levies at $5 per $1,000 real market value; Lane County operates under this framework with a January 2 through April 1 appeal window.
5. Appraisal Institute - cost of residential appraisals, fee survey context: Licensed residential appraisals in major metro markets like King County typically run $500 to $900 for a single-family home; contingency property tax firms commonly charge 25 to 40 percent of first-year savings.
6. Washington State Legislature - RCW 84.36.381, Senior and disabled exemption: Under RCW 84.36.381, qualifying seniors (61+) and disabled persons with household income at or below $84,000 receive a property tax exemption and value reduction in three income tiers.
7. Washington State Department of Revenue - Current Use and Open Space programs: Washington's Open Space, Farm and Agricultural, and Timber Land programs value qualifying land at its current use rather than its highest and best use.
8. Washington State Board of Tax Appeals - appeal of Board of Equalization decisions: A Board of Equalization decision can be appealed to the Washington State Board of Tax Appeals within 30 days of the decision.
9. Washington State Department of Revenue - Property Tax statistics and levy rates: King County effective property tax rates for a median single-family home have historically run between roughly 0.8 and 1.1 percent of assessed value, varying by city and taxing district.
10. Washington State Constitution - Article VII, Section 2, levy limitations: Washington's constitution caps total combined regular property levies at $10 per $1,000 of assessed value; the legislature has further limited state and local regular levies to $5.90 per $1,000 combined.
11. King County Treasury Operations - tax payment due dates and interest rates: King County property taxes are due April 30 (first half) and October 31 (second half); late payments accrue 1 percent monthly interest plus a 3 percent penalty.