King Property Tax: Rates, Deadlines & BOE Appeals (2026)

The 2026 King County assessment appeal deadline is July 1, 2026, or 60 days from the mailing date on your Official Property Value Notice, whichever is later. Because King posted 2026 residential notices mailed on June 18, July 16, and July 23, the next known residential deadlines as of July 30, 2026 are August 17, September 14, and September 21, 2026—check your parcel’s notice date before relying on any countywide date.

File real-estate appeals with the King County Board of Appeals and Equalization, online through eAppeals or by mailing/hand-delivering the Real Property Petition to the King County Board of Appeals and Equalization to 516 Third Avenue, Room/#1222, Seattle, WA 98104. The Board says petitions are not accepted by email.

How assessments work in King

King County values residential property every year at market value—what a willing buyer would pay a willing seller. For taxes paid in a given year, most properties are valued as of January 1 of the prior year; the current appeal cycle is the 2026 assessment roll for taxes payable in 2027, meaning the value date is January 1, 2026.

Washington requires annual revaluation, and King County also physically inspects about one-sixth of properties each year—roughly 100,000 parcels—to verify characteristics such as condition, size, additions, and property details. For 2026, the Assessor posted residential physical-inspection areas and a separate page of 2026 residential notice mailing dates.

Your assessment is not your tax rate. King collects for the state, county, cities, schools, port, EMS, flood, Sound Transit, and other districts. King’s 2026 property taxes total about $8.4 billion, up about 10% from 2025, while total county property value rose about 5.4%. The county says voter-approved levies, not simply rising home values, drive much of the tax increase.

Whether you should appeal

Appeal if you can show the Assessor’s value is higher than true and fair market value as of the valuation date. The Board will not reduce a value just because your tax bill rose, your assessment rose faster than your neighbor’s, you are on a fixed income, or you think taxes are generally too high.

The strongest homeowner evidence in King County is local, market-based evidence:

• comparable sales near your home, preferably close to January 1, 2026;
• a recent arm’s-length sale of your own property;
• an independent appraisal tied to the valuation date;
• contractor estimates for serious repairs that existed on the valuation date;
• photos, maps, easements, wetlands, steep-slope limits, access problems, or other value impacts;
• proof that the Assessor has wrong characteristics, such as finished square footage, bedroom/bath count, condition, or lot constraints.

King’s appeal page says about 25% of appealed property values result in some type of reduction. An older King County Auditor review found that across 2012–2017 appeals, about 40% of filers received a valuation and tax-bill reduction, but use the current 25% figure for expectations.

Before filing, check relief programs. Washington does not have a broad “homestead exemption” like some states, but King homeowners should check the Senior Citizen/Disabled Persons/Disabled Veterans exemption. For 2026 property taxes, King lists a household income limit of $84,000 based on 2025 income, with age/disability and occupancy rules. Limited-income deferrals have a September 1 application due date. There is also a home-improvement exemption and relief for destroyed property in specific situations.

A realistic savings example: suppose a Seattle home is assessed at $900,000, but your comps support $850,000. Using Seattle’s 2026 levy rate of 9.90845 per $1,000 of assessed value, a $50,000 reduction is worth about $495 for that tax year: $50,000 ÷ 1,000 × 9.90845. Your actual 2027 savings will depend on your 2027 levy code and tax rate, which are not set when you file a 2026 assessment appeal.

Step-by-step how to file

1. Wait for the Official Property Value Notice. King says to file after you receive the notice. The hard rule is the later of July 1 of the assessment year or 60 calendar days after the notice mailing date. For notices mailed June 18, 2026, the 60-day date is August 17, 2026. For July 16 notices, it is September 14, 2026. For July 23 notices, it is September 21, 2026.

2. Look up your parcel. Use King County eReal Property to confirm the Assessor’s value, property characteristics, levy code, sale history, and appeal due date. If the issue is a clear data error, contact the Assessor first at 206-296-7300 or Assessor.Info@KingCounty.gov; you may not need a formal appeal if they correct it.

3. Use the right form. For a house, condo, vacant land, or other real estate, use Real Property Petition to the King County Board of Appeals and Equalization. The forms page also lists Personal Property Petition, Current Use Petition, Exemption Petition, Hearing Participation Form, and Authorization of Agent Form. File a separate petition for each parcel.

4. Include the required items. A complete petition needs the parcel number, taxpayer name and address, representative/agent if any, property description, Assessor’s value, your requested value, specific reasons the value is wrong, your signature/date, and a copy of the value notice or determination.

5. File online or on paper. For real property, eAppeals is the fastest option and gives a confirmation within 24 hours. By mail or hand delivery, send the petition, attachments, and evidence to: King County Board of Equalization, 516 Third Avenue, Room/#1222, Seattle, WA 98104. The Board’s forms page lists the contact address as 516 3rd Avenue, Room 1222, Seattle, WA 98104-2306. The Board states it does not accept petitions by email. There is no county filing fee stated in the official petition instructions.

What happens after

The Board reviews your filing and marks it pending, complete, or active. If accepted, you will receive hearing information; King warns this can take six months or more because of appeal volume.

The Assessor sends a response at least 21 business days before the hearing, and your evidence is also due at least 21 business days before the hearing. If you miss that evidence deadline, the Board may reject the late evidence, continue the hearing, or take another procedural step.

Hearings are usually by phone, and King also allows an administrative review hearing, where the Board decides from the submitted materials without your participation. In a regular hearing, you and the Assessor’s representative present testimony, review evidence, and can question or refute each other’s arguments. King says the Board allows 40 minutes per appeal.

The Board sends a written Board Order within 45 days after the hearing date. If the value is reduced, Assessor records are adjusted; the Treasurer may issue a revised bill before the April 30 or October 31 tax due dates, or a refund if you already paid. If you or the Assessor disagree, either side may appeal to the Washington State Board of Tax Appeals within 30 days of the Board Order’s mailing date.

Local tips

Use King County’s free Property Tax Advisor before paying anyone. The office is independent of the Assessor and Board, helps residential owners identify comparable sales and prepare stronger appeals, and can be reached at taxadvisor@kingcounty.gov or 206-477-1060.

Do not build your case around assessment percentage increases. Build it around what your home would have sold for on January 1, 2026. In King County, the best comparables are usually same neighborhood, similar lot utility, similar living area, similar age/condition, and sales closest to the valuation date.

Finally, keep paying taxes on time even if your appeal is pending. The 2026 first half was due April 30 and the second half is due October 31; an appeal does not pause interest or penalties.

King Property Tax Rate

There is no single countywide 2026 property-tax rate for King County; the official Assessor schedule lists levy-code rates per $1,000 of assessed value. Examples from the 2026 schedule include Seattle levy code 0010 at 9.90845 per $1,000 AV and Bellevue levy code 0300 at 7.42658 per $1,000 AV; homeowners should use the levy code/rate shown for their parcel in the Assessor record.

Source: https://kingcounty.gov/en/dept/assessor/buildings-and-property/property-value-and-information/reports/levy-rate-reports/-/media/king-county/depts/assessor/buildings-property/reports/levy-rate-info/collective-rates-by-city-and-school-district/taxrate26.pdf

When Are Property Taxes Due in King?

Property taxes are paid in two installments: first half due April 30 each year and second half due October 31 each year; if a date falls on a weekend or King County holiday, payment is due the next business day. For 2026, the second-half October 31 date falls on a Saturday, so the next-business-day rule applies. Two installments: first half by April 30 and second half by October 31; if the tax is less than $50, the full payment is due April 30.

This is not the same as the assessment appeal deadline above. The appeal deadline is your window to contest your assessed value; the payment due date is when the resulting tax bill must be paid. Missing one does not affect the other, but missing either has real consequences — one forfeits your right to appeal for the year, the other can trigger penalties and interest.

Source: https://kingcounty.gov/en/dept/executive-services/buildings-property/treasury-operations/property-tax/faq

Property Tax Exemptions in King

• Senior citizens, people with disabilities, and disabled veterans property tax exemption — Owner-occupants of a primary residence who meet the income limit and meet at least one age/disability/veteran criterion; King County materials state annual household income under $84,000 for 2024-2026 property-tax years and eligibility for seniors, disabled persons, or veterans with at least an 80% total disability rating/100% VA compensation rate.. Freezes the value of the Washington State residence for property-tax purposes and exempts the property from all excess and special levies and possibly regular levies; applies to the primary residence and up to one acre. Yes; online or paper application. Renewal/reapplication is required at least once every 6 years, and changes in status or income must be reported. Apply by Applications must be received within three years of the property tax due date to be eligible for a refund of excess taxes paid; otherwise leave-specific annual timing to the Assessor.. (Source: https://kingcounty.gov/en/dept/assessor/buildings-and-property/property-taxes/tax-relief/senior-or-disabled-exemptions)
• Senior citizens and people with disabilities property tax deferral — Homeowners age 60 or older or retired because of physical disability who own and occupy the home, meet equity requirements, and meet the applicable King County income threshold; King County lists 2025 household income of $88,998 or less for this deferral page.. Defers property-tax liability; deferred taxes and interest become a lien on the property until repaid. Yes; application/deferral paperwork required. (Source: https://kingcounty.gov/en/dept/assessor/buildings-and-property/property-taxes/tax-relief/senior-or-disabled-exemptions)
• Homeowners with limited income property tax deferral — Homeowners who have owned the property for at least 5 years, live in the home as of January 1 of the current year, occupy it at least 6 months during the application year, have annual household income of $57,000 or less for the previous year, and meet equity requirements.. The Department of Revenue pays 50% of the property taxes on the homeowner's behalf; this is a deferral, not an exemption or grant, and deferred taxes/interest become a lien until repaid. Yes; must reapply each year and pay the first-half taxes before applying for deferral of the second installment. Apply by September 1 each year.. (Source: https://kingcounty.gov/en/dept/assessor/buildings-and-property/property-taxes/tax-relief/limited-income-deferral)
• Destroyed property relief — Real or personal property destroyed in whole or in part, or in a Governor-declared natural disaster area, where the property's value dropped by more than 20%. Involuntarily destroyed property may be eligible in the year of destruction; voluntarily destroyed property may be eligible the following year.. Reduction/refund is determined by the Assessor and Treasurer based on the value loss and timing; if taxes were already paid, the county refunds the determined amount. Yes; file the King County destroyed property form/claim with supporting documentation. (Source: https://kingcounty.gov/en/dept/assessor/buildings-and-property/property-taxes/tax-relief/destroyed-property-relief)
• Current use programs: farm and agriculture, designated forest land, open space/resource conservation — Property owners preserving qualifying open space, farmland, or forest land; designated forest land requires 5 or more acres used in commercial growing and harvesting of trees and an approved forest management plan.. Qualifying land is valued at current use rather than highest and best use, reducing property taxes compared with ordinary valuation. Yes; classification application required. King County lists application fees of $181 for farm and agriculture and no fee for designated forest land. (Source: https://kingcounty.gov/en/dept/assessor/buildings-and-property/property-taxes/tax-relief/current-use-programs)
• Home improvement exemption for physical improvements to a single-family dwelling — Existing single-family dwellings, including qualifying attached or detached accessory dwelling units, with qualifying remodels/additions that add value; normal maintenance and certain outbuildings/pools/fences do not qualify.. If approved, the exemption provides property tax relief for 3 years and may not exceed 30% of the assessed value of the improvement in the year construction began; only one home improvement exemption is allowed every 5 years. Yes; application must be filed before completion of construction, followed by written notice of completion. Apply by File before construction is complete; applications received by July 31 start with the following tax year, and applications after July 31 start with the second future tax year.. (Source: https://kingcounty.gov/en/dept/assessor/buildings-and-property/property-value-and-information/-/media/king-county/depts/assessor/documents/Forms/ExemptionForms/HIExemptionApplication.ashx)

How to Look Up Your Property Record in King

You can look up your property's official record at https://blue.kingcounty.com/Assessor/eRealProperty/default.aspx. King County Assessor eReal Property Search lets users look up parcel/account information by parcel number or address and view valuations, property characteristics, levy rates, and sale history.