Start with the value, not the tax increase
A tax bill can rise because of levies, budgets, and tax-rate changes even when the assessment is reasonable. The King County Board of Appeals and Equalization reviews whether the assessed value represents true and fair market value for the applicable valuation date.
Write down the county value and the lower value you believe the evidence supports. If the only argument is that the bill increased, the case does not yet identify a valuation error.
Run four checks on the parcel
The fastest screening process checks the public record before expanding into a full comparable-sales analysis. A single material record error can change which properties are genuinely comparable.
- Record check: verify living area, lot size, age, quality, condition, bedrooms, bathrooms, and property type.
- Sale check: compare arm's-length sales near the valuation date from the same market segment.
- Condition check: document defects, deferred maintenance, access limits, slope, noise, or other facts the mass-appraisal model may not see.
- Assessment check: review similar nearby properties, but use sales as the primary market evidence when reliable sales are available.
Decide whether the difference is supportable
A useful case has a requested value that follows from a coherent set of evidence. One unusually low sale or a distant lower assessment is usually less persuasive than several relevant sales with clear adjustments for material differences.
Also account for evidence that points upward. A balanced review prevents a homeowner from spending time on an appeal that the complete market record does not support.
Protect the deadline while you investigate
King County notices are mailed in area-based batches, so Seattle homeowners can have different practical filing dates. The county states that a petition is due by July 1 or within 60 days after the value notice is mailed, whichever is later.
Use the parcel's notice and the official filing system to confirm the date. Do not wait for a neighborhood article, a tax bill, or an informal review conversation to resolve the deadline for you.