King County publishes the outcome of every property tax appeal it decides, with the value before and the value after. It's a 130-page PDF that almost nobody reads. So we read all of it, looked up the property type behind all 3,467 parcel numbers, and pulled out the 951 cases that were actually houses.
Search for property tax appeal success rates and you'll find numbers running from 40 all the way to 90 percent. The National Taxpayers Union, which is really the source everyone cites, actually puts it at 30 to 50 percent nationally. Anything above that's basically somebody's marketing.
And counties hear appeals on every kind of property too, so the big commercial cases sit in the same record as the houses. In King County's 2024 record the appealed values run up to $652 million, the median is $1.5 million, and 36 percent of appeals are on property valued above $3 million.
So a single win rate across all of that describes office towers and apartment complexes about as much as it describes a house in Shoreline. We'd nearly published one ourselves before we caught it. Every figure below is single-family homes only.
| Decided in 2024 | Houses | Everything else |
|---|---|---|
| Appeals decided | 951 | 1,711 |
| Assessment left unchanged | 78% | 77% |
| Assessment reduced | 22% | 23% |
| Typical cut when reduced | 10.0% | 13.7% |
| Middle half of cuts fell between | 5.8% and 17.4% | 6.4% and 25.5% |
| Typical dollars off the assessed value | $146,000 | $651,500 |
| Typical value under appeal | $1,316,000 | $6,218,100 |
That second column covers apartment buildings, offices, warehouses, hotels, retail, vacant land and townhouse plats. It's there so you can see for yourself why mixing the two gives you a pretty misleading answer.
Of the 210 homeowners who won a reduction, 159 of them, about 76 percent, won because the assessor recommended the reduction. Only 51 won because the board overruled the assessor.
The county's record labels those two things separately. "Adjust to Asr Rec" means the assessor looked at the case and agreed to a lower number, usually before or at the hearing, and a plain "Adjust" means the board decided it.
Now for commercial owners the split looks quite different. Only 38 percent of their wins came from the assessor agreeing, so they really do fight it out. For homeowners, three out of four wins came from persuading the assessor rather than beating them.
Which means your evidence is worth the most early, in front of the person who actually set your value, rather than saved up for a hearing.
The typical successful homeowner appeal took $146,000 off the assessed value. And King County's 2026 levy rates run from about $8.59 to $10.58 per $1,000 of value depending on where you live, so that reduction works out to roughly this much.
| City | 2026 rate per $1,000 | Saved in year one |
|---|---|---|
| Renton | $10.58 | $1,544 |
| Shoreline | $9.95 | $1,453 |
| Seattle | $9.91 | $1,447 |
| Kent | $9.45 | $1,380 |
| Bellevue | $8.59 | $1,254 |
Filing doesn't cost anything in King County. So the honest way to think about it is that roughly one in five homeowners who sees it through gets somewhere around $1,400 a year, and four in five spend their time and get nothing.
Now we also read dozens of written decisions from Washington's Board of Tax Appeals, which hears cases from every county in the state and explains what it's thinking in a way the county record never does.
The board's looking at whether the whole range of your comparable sales sits below the assessed value. When an owner's sales run from say $830,000 to $904,000 and the county has the home at $972,000, those sales support a lower value and they don't support the assessment. That's a winning case.
But when the combined range of both sides' sales covers the assessed value as well as the owner's number, the board sustains, because nothing's been clearly disproved. Washington requires "clear, cogent and convincing" evidence to overcome the assessor's value (RCW 84.40.0301), and that's a really high bar compared to an ordinary dispute.
But one thing that does work is photographs of specific defects. In a 2026 case, photos of cracked window frames led the assessor to lower the home's condition rating outright.
A petition that says only that your value is too high gets thrown out as incomplete (WAC 458-14-056). The reasons box has to say something specific about why the number doesn't reflect what the home would actually sell for.
That's the whole question, and it's worth answering before you spend an afternoon on any of this. If those sales didn't close below your assessed value, then then honestly no amount of paperwork is going to help, because the county's going to show the board the same sales you're looking at.
And our free check does exactly that, using the assessor's own comparable sales search, and it tells most people not to bother.
Every figure above comes from a public document you can go read yourself.
If you spot an error in any of this, please write to hello@propertytaxbuddy.com and we'll correct it and say what changed.