King County Property Taxes, Explained for Buyers
Property tax is the biggest recurring cost of ownership after your mortgage — and in King County it works differently than most people assume. Your bill is not simply 'rate × price', assessments rising 20% doesn't mean your tax rises 20%, and there are real exemptions many owners never claim. Here's how it actually works.
How your King County tax bill is calculated
The King County Assessor revalues every property annually at 100% of estimated market value, using sales of comparable homes in your area. Your tax is that assessed value multiplied by the combined levy rate of every taxing district your home sits in — the state school levy (usually the biggest slice), your city, local school district, fire, library, EMS, and any voter-approved measures.
Because levy stacks differ by city and school district, effective rates across King County typically land between roughly 0.8% and 1.1% of assessed value. On an $800,000 home that's roughly $6,400–$8,800 a year, or $530–$730 a month on top of your mortgage payment.
- Look up any home's current assessed value and tax history free on the King County Assessor's eReal Property site before you offer.
- Assessed value often lags what you pay for the home — expect the assessment (and your bill) to catch up to your purchase price over the following cycle.
- Your lender usually collects 1/12 of the annual tax with each mortgage payment and pays the county from escrow.
The 1% rule: why rising values don't mean matching tax hikes
Washington limits how much most taxing districts can grow their regular levy budget: about 1% per year plus new construction, regardless of how much home values rise. When values jump, rates generally fall to offset — your bill mostly changes based on how your home's value moved relative to your neighbors', and on new voter-approved levies, not raw appreciation.
When taxes are due (and what happens at closing)
King County property taxes are billed in two halves: the first due April 30 and the second due October 31. At closing, escrow prorates taxes to the day — the seller pays their share of the year through closing, and you take over from there, so you never pay for the seller's months.
Exemptions and relief programs worth checking
Washington offers a senior citizen and disabled persons exemption (age 61+, or disabled, with household income under a King County-specific threshold that adjusts periodically) that can substantially reduce or freeze taxes. There's also a three-year home improvement exemption that keeps qualifying remodel value off your assessment, and a deferral program for eligible owners.
- Apply through the King County Assessor — exemptions are not automatic.
- If you're buying for an aging parent, the senior exemption can change the affordability math meaningfully.
How King County compares to neighbors
Effective rates in Pierce and Snohomish counties often run somewhat higher than close-in King County cities, though home prices are lower — so the dollar bills can still be smaller. Use our free Washington property-tax calculator to compare a real bill in Seattle vs. Renton vs. Tacoma vs. Everett on the price band you're shopping.
Official sources
This information is for education only — it is not financial, legal, or tax advice. Loan rates, program rules, and limits change; always verify current details with a licensed lender, your agent, and official sources before making decisions.