Washington assesses homes at 100% of market value and revalues every parcel annually, so your property tax bill is that assessed value multiplied by the combined rate of every taxing district your address sits in — city, school, fire, library, and others. A much-quoted "1% cap" limits how fast a taxing district's total levy can grow, but it does not cap your individual bill: new construction, voter-approved levies, and your home's own revaluation can all push your number up faster than 1% in a given year. Here's how assessed value, the levy cap, due dates, and King County's senior exemption actually work.
How King County arrives at your assessed value
Under state law (RCW 84.41.030), the county assessor must revalue every taxable parcel each year and physically inspect it at least once every six years. In practice, King County's appraisers walk roughly one-sixth of the county's parcels — about 100,000 homes — every year on a rotating area-by-area schedule, comparing each property's exterior and recorded characteristics against recent sales in the neighborhood. The assessed value that comes out of that process is meant to represent 100% of the property's true and fair market value, not some fraction of it, which is a different approach than some other states use.
That means your assessed value should track the local market reasonably closely, but it's a snapshot — it won't instantly reflect a hot few months of sales activity, and it can lag or overshoot the current market in either direction depending on when your area was last walked.
Why the "1% cap" doesn't cap your actual bill
Washington's RCW 84.55.010 limits how much a taxing district's total regular levy can increase year over year — generally 1%, or the rate of inflation if that's lower, for larger districts — without a vote. It's a real and meaningful limit on local government, but it applies to the district's aggregate collection, not to what shows up on any one homeowner's bill. Three things routinely push an individual bill above 1%:
- New construction is added to the district's levy base on top of the 1% growth allowance, so a fast-growing area can see levy totals rise faster even while staying within the letter of the cap.
- Voter-approved levies and bonds — school maintenance and operations levies, fire district levies, library bonds, and similar measures — aren't subject to the 1% limit at all, because voters approved them directly.
- Your home's own revaluation determines your share of a capped district total. If your assessed value rises faster than the countywide average for your district, your share of that fixed (or 1%-higher) pool of tax dollars grows — meaning your bill can jump well past 1% even though the district's total levy didn't.
There's also a separate, broader backstop: the Washington Constitution limits the combined rate of all regular, non-voter-approved levies on a property to $10 per $1,000 of assessed value. Voter-approved excess levies and bonds sit outside that ceiling too.
When property tax is due, and how it's prorated at closing
Washington splits the annual property tax bill into two installments under RCW 84.56.020: the first half is due April 30 and the second half is due October 31. If your total annual bill is under $50, the full amount is due by April 30 instead. Miss a deadline and interest and penalties accrue on the unpaid balance.
When you buy a home mid-year, you don't pay a full year's tax out of pocket — escrow prorates the current year's bill between buyer and seller based on how many days each of you owned the home around the closing date, with the seller crediting you for their share (or vice versa, depending on what's already been paid). From there, if you have a mortgage, your lender typically collects roughly one-twelfth of the estimated annual tax with each monthly payment and holds it in an escrow/impound account, then pays the county directly each April and October. That escrow reserve is part of what you'll see called out separately in your closing costs — see our closing costs guide for the full breakdown of prepaids and reserves.
Property tax is also a separate thing from Washington's real estate excise tax (REET), a one-time tax on the sale itself that's typically paid by the seller at closing — our REET guide explains how that one works if you want the distinction clear.
King County's senior and disabled exemption
If you're buying for a parent, helping an older relative downsize, or simply planning ahead, King County's Senior/Disabled Exemption can meaningfully reduce the property tax bill on a primary residence. To qualify, you generally need to:
- Be at least 62 years old in the first year you apply, or meet the county's disability criteria;
- Have owned the home as of December 31 of the preceding year;
- Have occupied it as your primary residence for at least six months of that preceding year; and
- Have annual income under $84,000 (the limit tied to 2025 income for the 2026 exemption), counting Social Security and most other income sources — though income from a qualifying service-connected disability doesn't count toward that limit.
King County also runs a separate property tax deferral program with a somewhat higher income ceiling for owners who qualify for the exemption but still need more relief. Applications go through the King County Assessor's Office, and because income limits and program details are set and updated by the county, confirm the current figures directly with the Assessor before counting on a specific number.
Checking the real number, and appealing an assessment
Because the combined rate depends on exactly which overlapping city, school, fire, and other districts an address falls into, there's no single "King County rate" you can apply to a listing. The only reliable way to see the real current assessed value and tax bill for a specific home is to look it up directly on the King County Assessor's property information site using the address or parcel number — don't rely solely on the tax-estimate figure shown on a Zillow or Redfin listing, since those can lag behind the most recent revaluation.
If you believe your home's new assessed value doesn't reflect its actual market value once you own it, you can appeal to the King County Board of Equalization. The petition must be filed (online or postmarked) by July 1 of the assessment year, or within 60 days of the mailing date printed on your valuation notice — whichever date is later.
Budgeting for property tax before you make an offer
Because your lender will build an estimated tax payment into your monthly mortgage payment through escrow, an unexpectedly high assessed value can change what a given home actually costs you each month — even at the same purchase price. Before writing an offer on a home that was recently renovated, newly built, or sitting in an area due for revaluation, it's worth pulling the current assessed value and tax bill from the county's parcel lookup rather than assuming last year's number (or a listing site's estimate) will hold. If you're earlier in the process, our first-time buyer guide for King County & the Eastside walks through budgeting, financing, and closing in order, and our mortgage pre-approval guide covers how lenders factor taxes and insurance into what you qualify to borrow.
A flat fee agent who flags this before you offer
Property tax rarely changes whether you should buy a home, but it should factor into what you offer and how you budget the monthly payment. A traditional buyer's agent charging roughly 2.5% commission on an $850,000 Eastside home costs about $21,250. A flat $2,999 buyer service provides the same core representation — offer strategy, negotiation, contract review, and closing support, including flagging a parcel's actual tax history before you offer — while leaving significantly more in your pocket for the down payment or closing costs. Compare the two in flat fee vs. a traditional buyer's agent.
General information, not legal or tax advice. Property tax assessment rules, levy rates, exemption and deferral income limits, and appeal deadlines are set by Washington state law and King County and are updated periodically — confirm current figures directly with the King County Assessor's Office or the Washington State Department of Revenue before making financial decisions. Shi Hao Liu is a licensed WA real estate broker (License #26003789) with Kelly Right Real Estate, not a tax professional or attorney. Verify any WA broker at the WA Department of Licensing.