When is the deadline to appeal in King County?
Washington law sets the appeal deadline at July 1 of the assessment year or 60 days after your value notice was mailed, whichever is later. King County uses the full 60 day window.
Here is the part that trips people up: King County revalues property area by area, and Official Property Value Notices mail in waves from roughly May through November. That means there is no single countywide deadline. Your deadline is 60 days from the mailing date printed on your own notice.
So if your notice arrives in August, your window runs into October. Check the mailing date on the notice the day it arrives and put the 60 day mark on your calendar. If you miss the window, the value stands for the year and your next chance comes with next year's notice.
For background, Washington revalues every property annually at 100 percent of market value as of January 1, with a physical inspection at least once every six years. The King County Department of Assessments handles valuations, and you can reach it at 206-296-7300 with questions about your notice.
How does the King County appeal process work?
Appeals go to the King County Board of Appeals and Equalization, not the assessor's office that set the value. You file a Real Property Petition, and there is no filing fee.
That separation matters. You are not arguing with the people who valued your home. The board is a separate body that weighs your evidence against the county's.
The typical path looks like this:
- Find the mailing date on your Official Property Value Notice and confirm you are inside the 60 day window.
- File through eAppeals, the county's online portal, where you can submit the petition, upload evidence, and track status. You can also mail or hand deliver a paper petition to 516 Third Ave, Room 1222, Seattle 98104. Emailed petitions are not accepted.
- State the value you believe is correct and attach your evidence, such as comparable sales and photos.
- Wait for a hearing to be scheduled. You can appear by phone or choose a records only administrative review where the board decides on the paperwork.
- Receive the board's written order, which is due within 45 days after your hearing.
What evidence do you need?
The burden of proof in Washington is on you, the taxpayer, and the legal standard is clear, cogent and convincing evidence. That sounds intimidating, but in practice it means showing the county concrete reasons your value is too high.
Aim your evidence at the valuation date. The 2026 tax roll reflects market value as of January 1, 2025, so sales from around that date carry the most weight. Organize everything into a clean packet a board member can follow in minutes.
The strongest evidence usually includes:
- Recent sales of comparable homes near you, ideally from around the January 1 valuation date
- Errors in the county's property record, like wrong square footage, bedroom count, or lot details
- Photos and repair estimates for condition problems the assessor could not see from the street
- A recent appraisal or your own purchase price if you bought recently
- Assessments of similar nearby homes that are valued lower than yours
How much money is at stake?
For the 2026 tax roll, based on January 1, 2025 values, residential assessments rose 5.54 percent on average countywide. The Eastside jumped 9.81 percent, Seattle rose 4.16 percent, southeast King County rose 5.42 percent, and southwest King County rose 1.95 percent.
Meanwhile total property taxes billed in 2026 hit $8.4 billion, up about 10 percent, roughly $770 million, over 2025, even though total assessed value rose only 5.4 percent. Most of that gap comes from voter approved levies and lid lifts, which is why bills can climb faster than values.
The median King County home is worth about $885,200, effective tax rates run roughly 0.82 to 0.91 percent, and the median bill is around $7,292 per year. At 0.82 percent, a $885,200 home pays about $7,260 a year, so winning a 10 percent reduction saves roughly $725 to $805 every year until the next revaluation catches up.
Remember that those percentage increases are averages. Mass appraisal models miss on individual homes in both directions, and an average increase in your area does not mean your specific increase was justified.
What happens after you file?
First, keep paying your tax bill on time. Filing an appeal does not pause or freeze what you owe, and if you win, the county refunds the difference.
Be patient on scheduling. Because of appeal volume, it can take six months or more for the board to schedule a hearing. Once the hearing happens, the written decision is due within 45 days.
If you disagree with the board's decision, you can appeal to the Washington State Board of Tax Appeals within 30 calendar days of the decision mailing date. That deadline has no extensions.
While you wait, nothing about the appeal changes your obligations. Taxes are billed and due on the normal schedule, so treat the appeal as a refund claim rather than a pause button.
Is appealing worth it in King County?
Filing is free, so the main cost is your time gathering comparable sales and preparing the petition. With a median bill above $7,000, even a modest reduction is real money, and larger Eastside increases in 2026 mean more homes than usual may be assessed above what the market supports.
It does take patience. Hearing waits can stretch past six months in high volume years. But the refund covers the full overpayment once a reduction is granted, so a slow win is still a win.
If you are 61 or older or retired due to disability, also look at the senior and disabled exemption. Households with 2025 income under $84,000 may qualify for relief on 2026 taxes, and the income thresholds rise for 2027 through 2029. An exemption can stack with a successful appeal.
If you would rather not build the case yourself, Homespring prepares the evidence, files the petition, and handles the hearing for you, with no upfront fee. Either way, check the mailing date on your notice as soon as it arrives, because the 60 day clock does not wait.