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Mercer Island, King County, Washington Property Taxes

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Property Taxes in Mercer Island, Washington

  • Median Mercer Island, Washington effective property tax rate: 0.66%, significantly lower than the national median of 1.02%, and lower than the Washington state median of 0.92%.

  • Median Mercer Island, Washington home value: $1,949,000

  • Median annual Mercer Island, Washington tax bill: $12,740, $10,340 higher than the national median property tax bill of $2,400.

How are property taxes in King calculated?

Property taxes in Mercer Island, Washington are calculated based on the tax assessed value, which is often lower than the actual market value due to property tax exemptions such as the homestead or senior exemption.

Understanding Mercer Island's property tax system, exemptions, and reduction opportunities can lead to significant savings. Regardless of where you live in Mercer Island, knowing local tax details benefits homeowners and investors.

Last Updated April 13, 2026

Mercer Island, King County, Washington Property Tax Bill Calculator

$100,000

$1,500,000

$3,000,000

Median Effective Tax Rate

0.66%

Estimate Property Tax Bill

$12,863

$11,937

SAVE WITH OWNWELL

$774

Average Annual Tax Savings

How Does the Mercer Island Property Tax Calculator Work?

Use this Mercer Island property tax calculator to estimate your annual tax bill. Enter your property's assessed value and our calculator applies Mercer Island's median effective tax rate of 0.66% — based on actual property records in King County — to generate your estimate.

Enter your property's estimated assessed value — the figure used to calculate your bill, which reflects any exemptions you hold and is typically lower than your home's market value. Our calculator applies Mercer Island's median effective rate across all local levies, providing a more accurate estimate than applying a single county millage rate.

Your bill may vary by ZIP code within Mercer Island: rates are 0.66% in 98040, with no variation shown in the available property records. That rate is lower than the Washington median property tax rate of 0.92%, but Mercer Island’s median property tax bill of $12,740 is still $10,340 higher than the state median bill.

If your estimate is higher than expected, Ownwell can appeal your Mercer Island assessment — you only pay if we save you money.

About Mercer Island Property Taxes

About Property Taxes in Mercer Island, King, Washington

Mercer Island’s median effective property tax rate of 0.66% is lower than the Washington state median of 0.92% and lower than the national median of 1.02%. This rate reflects the King County base levy combined with local school district levies and local improvement districts that vary by subdivision throughout the city.

Property tax rates are not uniform across Mercer Island. Homeowners in the 98040 ZIP code carry a median effective rate of 0.66%, while those in the same ZIP code pay 0.66%. This reflects how school district boundaries and local assessment districts are drawn across King County. Understanding which part of Mercer Island you live in can make a meaningful difference to your annual tax bill.

Mercer Island homeowners who believe their assessed value is too high can file a formal appeal with the Tax Assessor after the July notice date each year.

If your estimated bill above seems higher than expected, Ownwell can review your assessment and protest on your behalf. You only pay if we save you money.

Property Tax Rates Across Mercer Island, King County, Washington

As noted earlier, local government entities set tax rates, which can vary widely within a state.

Why? Because annually, each county estimates its required budget to provide services and divides that by the total value of all taxable property within its jurisdiction. This calculation results in the property tax rate.

While there are votes and laws involved in setting tax rates and budgets, in a nutshell, this is the annual process.

Below, you can compare Mercer Island's effective property tax rate to other cities in Washington and the median property tax rates in Washington and the U.S.

Property Tax Rates Across Mercer Island, King County, Washington

Source: Ownwell

0.63%

0.93%

1.24%

Our median effective property tax rate (tax bill Ă· assessor's market value) accounts for exemptions and deductions, making it more accurate than the general median tax rate, which is the midpoint of statutory rates before adjustments.

Median Effective Mercer Island Tax Rate

0.66%

Our median effective property tax rate (tax bill Ă· assessor's market value) accounts for exemptions and deductions, making it more accurate than the general median tax rate, which is the midpoint of statutory rates before adjustments.

Median Effective King County Tax Rate

0.99%

Median Effective Washington Tax Rate

0.92%

Median Effective United States Tax Rate

1.02%

Property Tax Rates Across Mercer Island, King County, Washington

Zip10th Percentile25th PercentileMedian Tax Rate75th Percentile90th Percentile
980400.65%0.66%0.66%0.66%0.66%

Source: Ownwell

Property Tax Assessment Values Across Mercer Island, King County, Washington

When examining property taxes in Mercer Island, Washington, understanding the distinction between market value and assessed value is crucial.

The market value is what a willing buyer would pay to a willing seller in an open and competitive market, often influenced by location, property condition, and economic market trends. The King County appraisal district estimates the market value for tax purposes.

The assessed value is the market value minus any applicable exemptions or limits determined by local laws and offerings. The tax assessed value is the figure used to calculate your property taxes or the amount multiplied by your tax rate to get your tax bill.

Assessment notices:

In King County, assessment notices are sent in the spring each year. They'll typically reach your mailbox by the middle of July.

Each property owner receives an assessment notice that contains both the market value and assessed value, along with an estimate of your property tax bill. By providing insights into how assessed and market values are determined, this section helps property owners navigate their tax responsibilities and understand the valuation processes affecting their property taxes in Mercer Island.

For example, the median home price in Mercer Island is $1,949,000, with tax bills ranging significantly across the county. 98040 has the highest median home price at $1,949,000.

Property Tax Assessment Values Across Mercer Island, King County, Washington

Source: Ownwell

$275,000

$3,858,750

$7,442,500

Median Mercer Island Market Value

$1,949,000

Median King County Market Value

$774,000

Median Washington Market Value

$501,600

Median United States Market Value

$235,294

Property Tax Assessment Values Across Mercer Island, King County, Washington

Zip10th Percentile25th PercentileMedian Home Price75th Percentile90th Percentile
98040$1,095,900$1,556,000$1,949,000$2,604,000$3,874,000

Source: Ownwell

Property Tax Bills Across Mercer Island, King County, Washington

Property tax bills in Mercer Island are based on the assessed market value of a home and the local tax rate set by taxing authorities in King County. When a home’s assessed value rises, the property tax bill can increase, even if the homeowner’s income does not. For Mercer Island homeowners, the median home price is $1,949,000, and the median property tax bill is $12,740 in ZIP code 98040. That is well above the national median property tax bill of $2,400 and reflects the area’s high home values.

Your bill is determined by the value assigned to your property and the levies applied to it, so similar homes can still have different tax bills. Homeowners at the 25th percentile pay $10,103, while those at the 75th percentile pay $17,030 and the 90th percentile pay $25,236. Ownwell can help homeowners review their assessed value, identify opportunities to appeal, and pursue exemptions that may lower property tax bills.

Property Tax Bills Across Mercer Island, King County, Washington

Source: Ownwell

$2,643

$24,618

$46,592

Median Mercer Island Tax Bill

$12,740

Median King County Tax Bill

$7,644

Median Washington Tax Bill

$4,512

Median United States Tax Bill

$2,400

Property Tax Bills Across Mercer Island, King County, Washington

Zip10th Percentile25th PercentileMedian Tax Bill75th Percentile90th Percentile
98040$4,639$10,103$12,740$17,030$25,236

Source: Ownwell

Don't miss the deadline to appeal!

Frequently Asked Property Tax Questions in Mercer Island, Washington

How are property taxes calculated in Mercer Island, Washington?
Property taxes in Mercer Island, Washington are calculated by multiplying your property's assessed value by the applicable tax rate set by local taxing authorities. The assessed value is determined by the county assessor and may differ from your property's market value depending on local assessment ratios and exemptions.
How do I appeal my property taxes in Mercer Island, Washington?
To appeal your property taxes in Mercer Island, Washington, you typically need to file a formal protest or appeal with your local appraisal district or assessor's office by the stated deadline. You'll need evidence such as comparable sales, a recent independent appraisal, or documentation of property condition issues. Ownwell can handle this entire process for you.
What property tax exemptions are available in Mercer Island, Washington?
Common property tax exemptions in Mercer Island, Washington include homestead exemptions for primary residences, senior citizen exemptions, veteran exemptions, and disability exemptions. Exemption amounts and eligibility requirements vary by county. Contact your local appraisal district or check Ownwell for details specific to your property.
When are property taxes due in Mercer Island, Washington?
Property tax deadlines in Mercer Island, Washington vary by county but typically include an assessment notice period in spring or early summer, followed by an appeal deadline, and a tax payment due date in the fall or winter. Check with your county assessor's office for specific dates in your area.
How can Ownwell help reduce my property taxes in Mercer Island, Washington?
Ownwell provides professional property tax appeal services in Mercer Island, Washington. Our team analyzes your assessment, gathers evidence, files all paperwork, and represents you at hearings — all with no upfront cost. You only pay a percentage of your savings if we successfully lower your tax bill.