King County Property Tax Appeal Guide

At a glance

King County uses mass appraisal to value over 700,000 parcels annually. The county targets 100% of market value as of January 1. When a market moves fast, as Seattle's did between 2020 and 2023, assessed values can lag on the way up and then overshoot as the market cools. Homeowners who bought in 2021-2022 at the peak are among the most likely to be over-assessed today.

How the appeal process works

1. 1

   Receive your assessment notice

   King County mails assessment notices on a rolling basis throughout the year, depending on your area. The notice shows your assessed value for the upcoming tax year. Your 60-day appeal window starts from the date on that notice.

2. 2

   File a petition with the BOE

   Download and complete the petition form from the King County Board of Equalization website or file online. You need your parcel number, your assessed value, and the value you believe is correct. No fee to file.

3. 3

   Gather your evidence

   The strongest evidence is comparable sales: homes similar to yours that sold near January 1 of the assessment year for less than your assessed value implies. The BOE also considers your purchase price if you bought the home recently, and documentation of property condition issues.

4. 4

   Attend your hearing

   The BOE schedules a hearing after your petition is received. Hearings are typically 15-30 minutes and can be done by phone. You present your evidence, the county assessor's office may respond, and the board issues a decision.

5. 5

   Receive the decision

   The BOE sends a written decision. If they reduce your value, your tax bill is recalculated. If you disagree with the result, you can appeal further to the Washington State Board of Tax Appeals.

Common reasons to appeal

• +Your assessed value is higher than what comparable homes in your neighborhood recently sold for
• +You purchased your home after January 1 of the assessment year for less than the assessed value
• +Your home has significant deferred maintenance, damage, or condition issues the assessor could not observe
• +Your property records are inaccurate, such as the wrong square footage, lot size, or number of bedrooms
• +Neighborhood-level assessment increases outpaced actual market changes in your specific micro-area
• +You live in a neighborhood where values have softened since the assessment date

Frequently asked questions

Can I appeal every year?

Yes. King County reassesses annually, which means you can file a new appeal each year. If your value goes up again, you can challenge it again. Most homeowners do not appeal every cycle, but there is no rule against it.

What if I already paid my taxes?

Paying your taxes does not waive your right to appeal. If your appeal succeeds after you have paid, King County will apply the overpayment as a credit to your next tax bill.

Do I need to appear in person?

No. BOE hearings can be conducted by phone. Most petitioners choose the phone option. You will be notified of your hearing date and time in advance.

What is the senior exemption in King County?

Washington State offers a senior and disabled persons property tax exemption for homeowners 61 or older with a combined disposable income under $84,000 (as of 2026). The exemption freezes or reduces your assessed value for tax purposes. You apply through the King County Assessor's office.

What happens if the BOE denies my appeal?

You can appeal to the Washington State Board of Tax Appeals within 30 days of the BOE's decision. That process is more formal, but the right to appeal is preserved.

How do I find my parcel number?

Your parcel number is on your assessment notice and your property tax bill. You can also look it up on the King County Assessor's website using your address.