King County, WA — Property Tax Underwriting Guide
Washington · Annual market review
What this means for multifamily underwriting
King County (Seattle, Bellevue, Redmond) is one of the strongest multifamily markets in the western US, anchored by Amazon, Microsoft, and Boeing.
Transaction type breakdown
King County Assessor values all property annually at 100% of true and fair market value. Sale prices are primary evidence; the assessed value commonly moves toward a recent above-assessment sale price within 1-2 years.
Refinance does not affect assessed value.
Ownership transfer is market evidence and commonly influences the next annual assessment.
Tax appeal information
10.0 mill (1.0% effective on market value) is a mid-county estimate for King.
Guide review
County guidance last reviewed: June 15, 2026
Tax-rate scope: Tax-rate scope is not established as parcel-specific; confirm the parcel's taxing-authority stack.
Official sources: King County Assessor
Annual-market model is well established for King County; millage is a mid-county estimate.
Parclio estimates are underwriting guidance, not legal or tax advice. Always verify millage rates, the seller's assessed value, and appeal deadlines with the county assessor or local counsel before relying on these numbers for a credit decision.
Run a tax reset estimate for King County
Use Parclio's estimator to model the post-closing tax bill, NOI impact, DSCR change, and underwriting memo language for your next King County deal.