King County Property Tax Appeal Guide
Everything you need to appeal your King County property tax assessment. Updated for 2026.
How King County Assesses Your Property
The King County Department of Assessments determines the value of all property in the county for tax purposes. Here's how it works:
Assessment Ratio: 100% of Market Value
Washington State law requires property to be assessed at 100% of true and fair market value as of January 1 of the assessment year (RCW 84.40.030). Your assessed value should equal what your home would sell for on the open market.
Assessment Cycle: Annual
King County reassesses all properties every year. The Assessor uses a mass appraisal approach — computer models analyze recent sales, property characteristics, and market trends to estimate values for all 524,000+ residential properties at once.
When Notices Are Mailed
Assessment change notices are typically mailed February through March. You have 60 days from the mailing date to file an appeal, but July 1 is the hard cutoff — you cannot appeal after July 1 regardless of when your notice was mailed.
What Gets Assessed
Your property assessment has two components:
- Land value — based on location, lot size, zoning, and comparable land sales
- Improvement value — based on building size, age, condition, quality, and features
The total assessed value (land + improvements) is what your property taxes are based on.
Why Assessments Can Be Wrong
Mass appraisal models work with averages. They can miss:
- Deferred maintenance or needed repairs
- Noise, traffic, or environmental issues affecting your property
- Incorrect property data (wrong square footage, bedroom count, etc.)
- Local market conditions that differ from the broader area trend
- Unique property features that reduce desirability
The Appeal Process
1. Review Your Assessment Notice
When you receive your assessment notice (February-March), compare the assessed value to what your property would actually sell for. The county assesses at 100% of market value as of January 1 of the assessment year.
Quick check: Use our free tool to instantly compare your assessed value to recent comparable sales.
2. Contact the Assessor (Optional but Recommended)
Before filing a formal appeal, consider calling the Assessor's office at (206) 296-7300. They can explain how they arrived at your value and correct any factual errors (wrong square footage, bedroom count, etc.) without a formal appeal. Many issues get resolved at this stage.
3. Gather Comparable Sales
Find 3-5 recent sales (within the last 12 months) of similar properties in your area. Good comparables match your property in size, age, condition, and location. Focus on sales that closed at prices below your assessed value.
4. Prepare Your Evidence
Your appeal packet should include:
- Valuation Evidence document — comparable sales analysis with adjustment grid showing market value is lower than assessed value
- BOE Petition Form — the official appeal form with your property info and opinion of value
- Photos (optional) — any property deficiencies, deferred maintenance, or issues affecting value
- Repair estimates (optional) — contractor quotes for needed repairs
5. File Your Appeal
You can file your appeal two ways:
Online (recommended):
- Go to King County eAppeals: blue.kingcounty.com/Assessor/eAppeals/
- Click "File a new appeal"
- Enter your parcel number
- Fill in the petition form (or upload your pre-filled form)
- Upload your valuation evidence document
- Submit — you'll receive a confirmation number
By mail:
Mail your completed petition form and evidence to:
Clerk of the Board of Equalization
King County Department of Assessments
516 3rd Avenue, Room 1211
Seattle, WA 98104
Must be postmarked by July 1.
6. Attend Your Hearing
The Board of Equalization (BOE) will schedule a hearing, typically within 6 months of filing. You can attend in person at the King County Administration Building or by phone.
What to expect:
- Hearings last 15-30 minutes
- You present your comparable sales and explain why the assessed value is too high
- The Assessor's representative presents their valuation
- BOE members may ask questions
- Be professional and stick to facts and data
7. Receive Decision
The BOE will mail their decision. If they agree your assessment is too high, your property taxes will be adjusted accordingly. If you disagree with the BOE decision, you can file a further appeal with the Washington State Board of Tax Appeals within 30 days.
What Evidence You Need
The BOE uses the "clear, cogent, and convincing evidence" standard (WAC 458-14-046). This means your evidence needs to clearly demonstrate that the assessed value exceeds fair market value. Here's what works:
Comparable Sales (Most Important)
Recent sales of similar properties are the strongest evidence. The BOE wants to see:
- 3-5 comparable sales within the last 12 months
- Properties similar in size, age, bedrooms/bathrooms, and location
- Sales that closed at prices below your assessed value
- Adjustments for differences between your property and the comps (size, age, lot, etc.)
Property Deficiencies
If your property has issues that reduce its value below what the assessor assumed:
- Deferred maintenance (roof, foundation, plumbing, electrical)
- Environmental issues (mold, asbestos, contamination)
- Noise or traffic exposure
- Steep slope, drainage problems, easements
- Functional obsolescence (outdated layout, systems)
Support deficiencies with photos, contractor estimates, and inspection reports.
Data Corrections
Check the Assessor's records for errors. Common mistakes include wrong square footage, incorrect bedroom/bathroom count, missing condition issues, or wrong year built. Verify your property record at King County eRealProperty.
Tips for a Strong Appeal
- Use recent sales — sales within the last 6-12 months carry the most weight
- Match property characteristics — similar size, age, beds/baths, and neighborhood
- Make adjustments — adjust comp prices for differences in size, lot, age, and features. This shows the BOE you've done rigorous analysis
- Document deficiencies — deferred maintenance, noise, slopes, or other issues that affect value
- Be specific — state exactly what you believe the land and improvements are worth
- Be professional — present facts and data, not emotions. The BOE responds to evidence, not complaints about taxes being too high
- Don't argue taxes — the BOE only decides assessed value, not tax rates or levy amounts
- Bring copies — bring extra copies of your evidence for the BOE panel members
- Keep it concise — you have limited time. Lead with your strongest comparable sales
Tax Exemptions in King County
Even if your assessment is accurate, you may qualify for exemptions that reduce your tax bill:
Senior Citizen Property Tax Exemption
Available to homeowners age 61 or older who meet income requirements.
| Income up to $58,423 | Full exemption (exempt from regular property taxes, 90% reduction) |
| $58,424 — $67,411 | Partial exemption (50% reduction) |
| $67,412 — $84,000 | Partial exemption (30% reduction) |
Income thresholds are for 2026 and include all household income.
Disabled Person Property Tax Exemption
Same income thresholds and reduction levels as the senior exemption. Available to homeowners who are disabled as defined by Social Security or the VA. Apply through the King County Assessor's office.
Disabled Veteran Property Tax Exemption
Veterans with an 80%+ service-connected disability rating may qualify for exemptions of 30% to 90% based on income. Surviving spouses of qualified veterans may also be eligible.
How to apply: Contact the King County Assessor's Exemption Unit at (206) 296-3920 or visit kingcounty.gov exemptions page. Applications are typically due by December 31.
King County Assessor Contact
| Department | King County Department of Assessments |
| Assessor | John Wilson |
| Phone | (206) 296-7300 |
| Address | 516 3rd Avenue, Room 708, Seattle, WA 98104 |
| Hours | Monday — Friday, 8:30 AM — 4:30 PM |
| Website | kingcounty.gov/assessor |
| Online Portal | eRealProperty Lookup |
Official Resources
- eAppeals Portal — File your appeal online
- eRealProperty — Look up your property's assessed value and details
- Exemptions & Deferrals — Senior, disabled, and veteran tax relief programs
- King County Assessor — Official department page
- Board of Equalization — Appeal hearing information and schedules
- RCW 84.40.030 — Washington State law on true and fair value assessment
Frequently Asked Questions
What is the deadline to appeal my property taxes in King County?
July 1 of the assessment year, or 60 days from the date your valuation notice was mailed, whichever is later. Assessment notices are typically mailed February through March, so the July 1 deadline applies to most homeowners.
How do I file a property tax appeal in King County online?
Go to the King County eAppeals portal at blue.kingcounty.com/Assessor/eAppeals/. Click "File a new appeal," enter your parcel number, fill in the petition form, upload your evidence documents, and submit. You'll receive a confirmation number immediately.
What happens at a Board of Equalization hearing?
You present your comparable sales evidence to a panel of BOE members. The Assessor's representative also presents their valuation. The hearing typically lasts 15-30 minutes. You can attend in person at the King County Administration Building (516 3rd Ave, Seattle) or by phone. The BOE will mail their decision afterward.
How much can I save by appealing my property taxes?
It depends on how much your property is over-assessed. At King County's effective tax rate of about 0.82%, every $10,000 reduction in assessed value saves approximately $82 per year. If your home is over-assessed by $50,000, that's about $410/year — or $2,050 over 5 years.
What evidence do I need for a King County property tax appeal?
The strongest evidence is comparable sales — 3 to 5 recent sales of similar properties that sold for less than your assessed value. You should also make adjustments for differences between your property and the comps. Additional evidence can include photos of property deficiencies, contractor repair estimates, or documentation of data errors in the Assessor's records.
Can I still pay my property taxes while my appeal is pending?
Yes, and you should. Filing an appeal does not suspend your tax obligation. Pay your taxes by the due date to avoid penalties and interest. If your appeal succeeds, you'll receive a refund or credit for the overpayment.
What is the difference between assessed value and market value?
Assessed value is the value the King County Assessor assigns to your property for tax purposes. Market value is what your property would realistically sell for on the open market. King County assesses at 100% of market value, so ideally they should be the same — but mass appraisal models often overestimate, creating grounds for appeal.
What are the odds my appeal succeeds?
King County homeowners win roughly half of BOE appeals. Your odds improve significantly when you present well-organized comparable sales evidence with proper adjustments. The BOE wants to see data, not opinions.
Do I need a lawyer or tax consultant to appeal?
No. Property tax appeals before the Board of Equalization are administrative hearings, not court proceedings. Most homeowners represent themselves. The key is having good comparable sales evidence — which is what our tool helps you create.
What if I disagree with the BOE decision?
You can file a further appeal with the Washington State Board of Tax Appeals within 30 days of the BOE decision. State-level appeals involve a more formal process and may benefit from professional representation.
Does filing an appeal risk raising my assessment?
Technically, the BOE can adjust your assessment in either direction. In practice, this is very rare. The BOE almost always either reduces the assessment or leaves it unchanged.
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