Every year, King County mails property tax assessment notices to homeowners. Most people file them away and pay without a second thought. But if your home's assessed value is higher than what it would actually sell for on the open market, you may be overpaying — and you have the right to appeal.
Step 1: Understand what you are appealing
The King County Assessor sets the assessed value of your home each year. Your property tax bill is calculated by multiplying that value by the local levy rate. If the assessed value is too high, you pay too much. The appeal process lets you challenge that number before the King County Board of Equalization (BOE).
Important: you are not appealing your tax rate or your tax bill directly. You are appealing the assessed market value the Assessor assigned to your home.
Step 2: Check whether you have a case
Before filing, compare your assessed value to recent sales of similar homes in your neighborhood. Look for homes that sold within the past 12 months, within roughly a mile of your address, with similar square footage, bedroom count, and condition. If those homes sold for meaningfully less than your assessed value, you likely have a case.
This is where most homeowners get tripped up. The burden of proof is on you — by law, the Assessor is presumed to be correct. If your comparable sales don't clearly support a lower value, the Board will side with the Assessor.
Step 3: File your appeal before the deadline
In King County, the appeal deadline is typically July 1 of the assessment year, or 60 days after your assessment notice was mailed — whichever is later. Miss this window and you cannot appeal until the following year.
You file your appeal with the King County Board of Equalization. The form requires your parcel number, the assessed value you received, and the value you believe is correct.
Step 4: Gather your evidence
The Board responds to one thing: market evidence. The strongest evidence is a list of comparable sales — recently sold single-family homes near yours with similar characteristics. Each comparable should include the sale date, sale price, address, square footage, and bedroom count.
- Sales within the past 12 months carry the most weight
- Homes within 0.5–1 mile of your address are most comparable
- Similar square footage (within 20%) is critical
- Condition and year built matter — a fully renovated home is not comparable to one that has not been updated
Step 5: Attend your hearing
The BOE will schedule a hearing, typically 30–90 days after you file. You present your evidence, the Assessor may respond, and the Board makes a decision. Hearings are informal — you do not need a lawyer. You do need clear, organized evidence.
What are the odds?
According to the King County Board of Equalization, approximately 25% of appeals result in some type of reduction. The cases that win are almost always backed by solid comparable sales data. Vague arguments or appeals filed without evidence rarely succeed.
At Appealo, we run the comparable analysis before recommending an appeal. If the numbers don't support a reduction, we tell you — because filing a weak case wastes your time and ours.
How Appealo helps
Appealo is a Bellevue-based service built specifically for King County single-family homeowners. Enter your address and we will analyze your home against recently sold comparable homes in your neighborhood, give you an honest assessment of your appeal viability, and file on your behalf for a flat $89 — no commission, no percentage of savings.