Across the United States, only about 3–5% of homeowners ever appeal their property tax assessment — but among those who do, 40–60% win a reduction, according to the National Taxpayers Union Foundation. The process is the same anywhere: check your data, gather comps, file before the deadline, and present a clean case. Here's the playbook.
Step 1: Decide if you have a case
Read your annual value notice carefully. Two signals strongly suggest an over-assessment:
- Year-over-year jump greater than ~15%. Bulk appraisal models occasionally over-shoot a neighborhood. A sudden spike with no comparable sales backing it is worth challenging.
- Recent nearby sales below your assessed value. If three similar homes within half a mile sold last year for less than the Assessor says yours is worth, you have evidence the model is off.
Step 2: Pull your property record and look for errors
Errors on your property record card — wrong square footage, wrong bathroom count, wrong year built, condition rated too high — are the single most common reason for over-assessment. Every county publishes the record online. Read every line. A 200-square-foot error on a $400/ sqft market can be worth $80,000 in assessed value.
Step 3: Build a comparable-sales analysis
Comparable sales — "comps" — are the heart of nearly every successful appeal. Pick 3–5 arms-length sales of similar properties from the 12 months ending on your jurisdiction's valuation date (January 1 in Washington). "Similar" means:
- Same neighborhood or school attendance zone
- Living area within roughly 20%
- Year built within roughly 10 years
- Same building grade and similar condition
- Same general lot character (no waterfront vs. interior mixes)
Then adjust each comp for differences: time of sale (use a local home price index), size, age, grade, condition, lot, and view. The average of the adjusted prices is your supportable market value.
Step 4: Check your deadline — twice
The deadline is printed on your assessment notice. It's non-negotiable. Most jurisdictions give you 30–60 days from the notice mailing date, sometimes anchored to a fixed calendar deadline. In King County, Washington, for example, the deadline is the later of July 1 or 60 days from the value-notice mailing date.
File at least a week before the deadline. Mail can be slow.
Step 5: Consider an informal review first
Many assessor's offices offer an informal review before you file a formal petition — usually by email or phone. Present your evidence; the appraiser reviews it; they may simply correct the record without a hearing. This is the path of least resistance. Informal reviews don't extend your formal-appeal deadline, so file the formal petition in parallel if you're close to the cutoff.
Step 6: File the formal petition
Most jurisdictions accept online filing. Your petition must state:
- Your opinion of value (a specific number)
- Specific reasons (errors, comps, conditions — not just "too high")
- Your evidence, attached
Some counties charge a small filing fee ($25–$50); many, including King County, charge nothing.
Step 7: Exchange evidence and prepare for hearing
Most boards require you to share your evidence with the Assessor in advance — King County's rule is 21 business days before the hearing. This is when most appeals settle. The Assessor reviews your comps and often agrees to a reduction without a hearing. If not, you'll get a short hearing (15–30 minutes) where you present, they respond, and the board decides.
Step 8: Wait for the decision — and lock in the savings
Decisions arrive in writing, typically within 30–60 days of the hearing. If you win, your new value becomes the baseline going forward — your savings recur every year until the next reassessment. If you lose, most jurisdictions allow one further appeal to a state-level board within ~30 days.
Two things that sink most appeals
- No comps, or weak comps. "My neighbor said his went down" is not evidence. Adjusted comparable sales are.
- Filing late. Boards have zero discretion on deadlines. Read your notice the day it arrives.
If you're in King County, this site auto-generates your complete comp-based analysis from official county data in 30 seconds. Pull your report and check whether the numbers support an appeal before you write anything.