Tax rates in King County stack across several systems. Sales tax on retail purchases lands between roughly 10% and 10.35% depending on the address. Property tax is not a single percentage but the sum of levies from the county, schools, fire districts, and other taxing bodies, applied to 100% of assessed value. Selling real estate triggers a graduated state Real Estate Excise Tax from 1.1% to 3.0%, plus a 0.5% local REET in almost every city. Washington’s capital gains tax adds 7% or 9.9% on large investment profits, though real estate gains are excluded. And many cities layer their own Business and Occupation tax on gross receipts.
Sales and Use Tax
Washington’s base sales tax is 6.5%, set by state law and collected on every retail transaction statewide.1Washington State Legislature. Washington Code 82.08.020 – Tax Imposed Retail Sales Retail Car Rental King County and its cities layer local taxes on top, pushing the total to roughly 10% to 10.35% depending on where the purchase happens.
The largest local piece is the Regional Transit Authority tax of 1.4%, which funds Sound Transit’s light rail, commuter rail, and express bus service.2Washington Department of Revenue. Regional Transit Authority (RTA) Tax – Section: What rate do I pay for RTA sales taxes? Smaller local components fund criminal justice, mental health, and public health. Individual cities can also adopt transportation benefit district taxes or housing levies, so two addresses a few miles apart can carry different rates.3Washington Department of Revenue. Local Sales and Use Tax
Which Address Sets the Rate
Washington uses destination-based sourcing. The rate on delivered goods is set by the delivery address, not the seller’s location.4Washington State Department of Revenue. Reporting Destination-Based Taxes Walk into a store and you pay the rate where the store sits. Have the same item shipped and you pay the rate at your home.
A few categories work differently. Motor vehicles, watercraft, aircraft, manufactured homes, and wholesale sales follow other sourcing rules. Most services are sourced where the work is performed rather than where the customer lives.4Washington State Department of Revenue. Reporting Destination-Based Taxes
Property Tax
Property tax in King County starts with budgets rather than a fixed percentage. Each taxing district — schools, fire, library, the county itself — calculates what it needs, and the rate is derived by dividing those budgets by the total assessed value in the district. When property values rise across the board while budgets stay flat, the rate per dollar of assessed value drops.
State law caps how much a district’s regular levy can grow. Without voter approval, the total levy can increase by no more than 1% per year, plus revenue from new construction.5Washington State Legislature. Washington Code 84.55.010 – Levy Rates Limit Factor That cap is a big part of why effective rates have stayed moderate even as home prices have climbed.
The King County Assessor sets fair market value for every property each year, and each property goes on the roll at 100% of that value.6Washington State Legislature. Washington Code 84.40.030 – Manner of Assessment of Real and Personal Property Your bill is the combined levy rate — quoted as a dollar amount per $1,000 of assessed value — applied to your assessment. If the combined rate is $10 per $1,000 and your home is assessed at $500,000, the annual tax is $5,000. That total is split among the taxing districts that overlap your parcel.7Washington State Legislature. Washington Code 84.52.010 – Levy Rates Limit on Aggregate Amount The state school levy is usually the biggest slice, often more than a third of the bill. Voter-approved bonds for schools, parks, or other capital projects add separate levies, which is why identical homes in different neighborhoods can owe noticeably different amounts.
Payment Deadlines and What Late Costs
Property taxes are due in two installments: the first half by April 30 and the second half by October 31. If you owe less than $50 total, the full amount is due April 30.8King County. 2026 Property Taxes
Missing a deadline triggers interest, and for some property types, penalties too. Residential parcels with four or fewer units are charged 9% annual interest on the delinquent balance and no flat penalties. Commercial real estate, residential buildings with five or more units, and personal property face 12% annual interest, a 3% penalty on June 1, and an additional 8% penalty on December 1.9Washington State Legislature. Washington Code 84.56.020 – Tax Delinquent Penalties and Interest After three years of delinquency, the county treasurer must begin issuing certificates of delinquency, which can lead to foreclosure.10Washington State Legislature. Washington Code Chapter 84.64 – Lien Foreclosure
Appealing Your Assessed Value
If you think the Assessor overvalued your property, you can petition the King County Board of Equalization. The deadline is July 1 of the assessment year or 60 days from the mailing date on your valuation notice, whichever is later.11King County. How to Appeal Your Valuation The state default is 30 days, but King County uses the maximum 60-day window the statute allows.12Washington State Legislature. Washington Code 84.40.038 – Appeal of Assessment Notices typically arrive between May and November, so check the mailing date on yours. Miss the deadline and you lose your right to appeal for that tax year.
Senior and Disability Exemption
Seniors and people with disabilities can qualify for a property tax exemption that meaningfully cuts the bill. To qualify for the 2026 tax year, you must meet all three of the following:
- You were at least 61 by December 31, 2025, or you had a qualifying disability or service-connected veteran’s disability as of that date.
- You owned and lived in the home as your primary residence for more than six months of the previous year.
- Your total household income, including a spouse, domestic partner, or co-owner living with you, was $84,000 or less after qualified deductions.13King County. Senior Exemption Portal
A surviving spouse or domestic partner of someone who held the exemption may also qualify if they were at least 57 during the year their partner died.13King County. Senior Exemption Portal
Real Estate Excise Tax When You Sell
Selling property triggers the Real Estate Excise Tax, a one-time tax due when ownership transfers. By law, the seller owes it.14Washington State Legislature. Washington Code 82.45.080 – Tax Obligation of Seller The state REET is graduated, so different slices of the sale price are taxed at increasing rates:15Washington State Legislature. Washington Code 82.45.060 – Tax on Sale of Property
- Up to $525,000: 1.1%
- $525,001 to $1,525,000: 1.28%
- $1,525,001 to $3,025,000: 2.75%
- Over $3,025,000: 3.0%
These thresholds adjust every four years based on the shelter consumer price index, with the next adjustment set for January 1, 2027.15Washington State Legislature. Washington Code 82.45.060 – Tax on Sale of Property
King County adds a local REET of 0.50% for nearly every city and unincorporated area. Only the town of Skykomish uses a lower 0.25% local rate.16Washington Department of Revenue. Local Real Estate Excise Tax (REET) Rates On an $800,000 sale, the state REET works out to $5,775 on the first $525,000 plus $3,520 on the next $275,000, for $9,295 in state tax, and another $4,000 in local REET at 0.50%.
Not every transfer is taxed. A genuine gift of real property, where nothing of value changes hands, generally is not subject to REET, though if the recipient assumes any of the seller’s debt, the tax applies to that debt relief.17Washington Department of Revenue. Real Estate Excise Tax Exemptions (Commonly Used)
Washington Capital Gains Tax
Washington taxes profits from selling long-term investments through what the state calls a capital gains excise tax. For 2026, the rates are tiered:18Washington Department of Revenue. New Tiered Rates for Washingtons Capital Gains Tax
- 7% on the first $1,000,000 of taxable long-term gains
- 9.9% on gains above $1,000,000
The tax applies to gains above an annual standard deduction that is adjusted periodically. Returns are due April 15, even if you file a federal extension.
Several categories are fully exempt, and one matters especially for King County property owners: real estate gains are not subject to this tax at all, and neither are gains attributable to real estate held through a private entity. Retirement account distributions, depreciable business assets, livestock used in farming, timber and timberlands, and commercial fishing privileges are also excluded.19Washington Department of Revenue. Capital Gains Tax In practice, this tax mostly hits gains from stocks, bonds, and ownership interests in businesses that do not derive their value from real estate.
City Business and Occupation Tax
King County itself does not impose a countywide B&O tax in unincorporated areas, but many cities within the county levy their own B&O tax on gross receipts. These are local taxes, separate from the state B&O tax, which runs on a different rate structure.
City B&O rates vary by municipality and by business activity. Businesses are classified as retailing, wholesaling, manufacturing, services, and so on, with a different rate for each class. Within a single city, the rate must be uniform across all businesses in the same class but can differ between classes.20MRSC. City Business and Occupation (B&O) Taxes – Section: B&O Tax Rates and Use of Revenues For retail activity, a city cannot set the rate above 0.2% of gross receipts without voter approval. Service businesses often face somewhat higher rates, with exact figures varying by city.
If your business operates in more than one city, you need to track revenue by location and file separately with each city where the work is performed. Seattle, the largest city in the county, has its own filing system.21Seattle.gov. Business Licenses