County assessor records are the public parcel file a county keeps on every property for the purpose of taxing it. For each parcel the record holds the owner of record, the mailing address the tax bill goes to, the assessed value of the land and the buildings, the physical characteristics, and the sale history. The assessor sets value; a different office, the treasurer, collects the tax. The records are free to search online in nearly every county, and they are the first stop for anyone trying to find out who owns a property or what it might be worth.
I run a tool that joins code enforcement records to the assessor roll for every parcel in seven Puget Sound markets, so I read assessor data in bulk. This page is the field-by-field version of what an investor actually uses, where the records come from, and where they mislead you. The wider map of property records is in our guide to public records for real estate.
What the county assessor does
The assessor's only job is valuation. Washington's RCW 84.40.030 requires that "all property must be valued at one hundred percent of its true and fair value in money," using sales of the property or similar properties within the past five years, or cost and income methods where sales are thin. The assessor does not set tax rates, does not collect payments, and does not record deeds.
Three other offices do the rest, and the split matters when you go looking for a document:
| Office | What it holds | What it does not hold |
|---|---|---|
| Assessor | Owner of record, mailing address, assessed value, parcel characteristics, sale history summary | The deed itself, tax payment status, liens |
| Recorder / Auditor | Deeds, mortgages, liens, easements, the full chain of title | Value, characteristics |
| Treasurer | Tax bills, payments, delinquency | Ownership detail beyond the billing name |
| City code enforcement | Violations, orders, complaints | Anything about ownership or value |
In some counties the assessor and treasurer are one elected office, which is why Pierce County calls it the Assessor-Treasurer. The data is still two systems.
The assessor's records are public because the valuation is appealable. RCW 84.48.150 obliges the assessor to hand any taxpayer "a compilation of comparable sales utilized by the assessor in establishing such taxpayer's property valuation." A roll that has to defend itself to every owner cannot be secret, and the same openness is what makes it the best free property dataset there is.
The fields, and what each one is good for
A parcel record runs to dozens of fields. These are the ones I read, in the order I read them.
| Field | What it is | How an investor uses it | Where it fails |
|---|---|---|---|
| Taxpayer name | The owner of record as the assessor last recorded it | Who to contact | Lags a sale or a death by months; shows an LLC or trust name, not a person |
| Mailing address | Where the tax bill is sent | The absentee test: mail address differs from the property means the owner does not live there | A property manager's address, or a stale one after a move |
| Situs address | The property's physical address | Matching to code cases, permits, and 311 | Unit numbers and directionals are inconsistent across systems |
| Parcel number (APN) | The county's unique ID | The join key for everything else the county publishes | Formats differ by county; what is an APN covers it |
| Assessed land + improvement value | The taxable value, set annually | A floor for a quick offer range; a land-heavy ratio flags a teardown | Set as of a fixed date, never sees inside the house |
| Year built, square footage, beds, baths | Physical characteristics from the last inspection | Rough rehab scoping and comp filtering | Unpermitted changes never make it in |
| Lot size, zoning | Land area and the zoning code | Development upside, DADU or lot-split potential | Zoning is often a link to the city's map, not a field |
| Sale history | Date, price, instrument, and reason code for recorded sales | Purchase basis, how long the owner has held, distress-coded transfers | Non-market transfers show $0 or a nominal price |
The mailing address is the field that earns its keep. On our Seattle roll, 178,268 of 181,996 parcels carry one, a 98% fill rate, and comparing it to the situs address is how we classify ownership posture. About 58% of the scored distressed-property leads in our database with a known posture are absentee-owned. How to find out who owns a property covers the mailing-address trap in detail: it tells you where the bill goes, not where the owner sleeps.
Assessed value is the field people over-trust. The assessor is required by RCW 84.41.030 to revalue every parcel annually but to physically inspect it only "at least once every six years." Between inspections the value moves with the neighborhood, not with the house. We measured the gap on 20,172 arm's-length Seattle sales: the median sale ran 1.075 times assessed, and houses under $500,000 sold at 0.853 times. Assessed value vs market value has the full breakdown. Treat the number as a floor and a filter, never as a price.
How to search county assessor records
Step 1: Find the portal
Every county runs one, and they are all free for single lookups. The three I use most:
| County | Portal | Search by | Bulk data |
|---|---|---|---|
| King County, WA | eReal Property | Parcel number or address | Full roll as downloadable extracts, plus a lookup table that decodes the sale codes |
| Pierce County, WA | Assessor-Treasurer parcel search | Parcel number, address, or owner name | Roll extracts on request and via the county's open data portal |
| Snohomish County, WA | Assessor property search | Parcel number, address, or owner name | SCOPI map plus downloadable sales and parcel files |
Property owner search by county lists more portals and the quirks of each. If the county's search is address-first, start there. If it is parcel-first, get the parcel number from the county GIS parcel map by clicking the lot.
Step 2: Search by address, then by parcel number if that fails
Assessor address matching is literal. "1st Ave" and "First Avenue" are different strings to it, and a unit number in the wrong slot returns nothing. When an address search fails, do not conclude the parcel is missing; find the parcel number on the map and search by that.
Step 3: Read the owner and the mailing address together
The taxpayer name is the owner as of the last recorded deed the assessor processed. Read the mailing address on the same screen. If the two addresses match, the owner probably lives there. If the mailing address is a PO Box, another city, or another state, you have an absentee owner, and that single field changes how you approach them. If the name is an LLC, the assessor has told you all it knows; how to find an LLC property owner picks up from the Secretary of State.
Step 4: Read the valuation and characteristics
Land value, improvement value, total, and the year they were set. Then year built, square footage, and lot size. A parcel where land is most of the total is a teardown candidate regardless of what the house looks like. A house with an improvement value that has not moved in years, on a street where everything else has, was last inspected a long time ago.
Step 5: Check the sale history and its codes
For older ownership or building changes, the current roll is only a starting point. Our guide to finding a property's history shows how to compare earlier assessment cards with deeds, permit files and dated photographs.
The assessor's sale history is the fastest way to see how long the owner has held and what they paid. King County also records a reason code and an instrument code on every sale. Most of the roll is ordinary warranty deeds. The exceptions, trustee's deeds, estate settlements, foreclosure-coded transfers, are distress markers that arrive at the assessor before they arrive anywhere convenient. How to do a title search explains what those instruments mean.
Step 6: Go to the bulk file when you need a list
The portal is built for one parcel at a time. Every assessor I have worked with also publishes the whole roll as a downloadable extract, usually a few hundred megabytes of CSV. That is where lists come from. Bulk property owner data covers the download-and-join workflow. One rule to know before you build on it: Washington's Public Records Act, at RCW 42.56.070(8), bars agencies from providing "lists of individuals requested for commercial purposes." Parcel data is not a list of individuals, and the roll is published openly, but the King County portal makes you acknowledge that clause before it searches, and a records request framed as "give me every owner's name for marketing" will be refused on it.
What the roll looks like at scale
Because we load the full roll for every market we cover, I can say how complete it actually is. Seattle, September 2026:
| Field | Parcels with the field populated | Share of 181,996 |
|---|---|---|
| Assessed value | 181,849 | 99.9% |
| Lot size | 181,930 | 99.9% |
| Mailing address | 178,268 | 98.0% |
| Year built | 160,588 | 88.2% |
Source: FlaggedLeads property table, King County Assessor roll for Seattle, counts as of September 26, 2026.
The missing year-built rows are mostly vacant land and condos where the county carries the value at the building level. The missing mailing addresses are the interesting 2%. A parcel with no billing address is one the county cannot bill cleanly, which is its own kind of signal.
That completeness is why assessor data is the spine of every property tool. Where property data tools get their data is the honest version: PropStream, BatchLeads, and the rest are reselling the same roll you can download, with the recorder and a skip trace layered on. What none of them join is the city's enforcement file, which is the part I built. Choose one metro and start a 14-day trial, with no card required.
Frequently asked questions
What does the county assessor do?
The county assessor values every parcel in the county for property tax purposes and maintains the public record of who owns it and where the tax bill is sent. The assessor does not set tax rates, collect taxes, or record deeds. In Washington the assessor must revalue every parcel each year and physically inspect it at least once every six years.
Are county assessor records public?
Yes. The parcel roll, including owner of record, mailing address, assessed value, and property characteristics, is public in every state and free to search online in nearly every county. Washington's Public Records Act restricts agencies from supplying lists of individuals for commercial purposes, but the parcel record itself is open.
How do I find who owns a property using the assessor?
Search the county assessor's parcel portal by the property address. The record returns the taxpayer name, which is the owner of record, and the mailing address the tax bill goes to. If the address search fails, find the parcel number on the county's GIS map and search by that instead.
What is the difference between the assessor and the treasurer?
The assessor sets the value. The treasurer sends the bill and collects the payment. To learn what a property is worth on the roll or who owns it, use the assessor. To learn whether the taxes are paid, use the treasurer. Some counties combine the two offices, but the records stay separate.
Is the assessed value the same as what a house is worth?
No. Assessed value is set once a year as of a fixed date, by mass appraisal, and the assessor may not have been inside the house for six years. On 20,172 arm's-length Seattle sales the median price was 1.075 times assessed value, and cheaper houses sold below assessed. Use the number as a floor and a filter, then price the house on comparable sales.
How often are assessor records updated?
Ownership and mailing address update when the assessor processes a recorded deed, usually within a few weeks to a few months of the sale. Values update annually. Physical characteristics update when the parcel is inspected or a permit closes, which can mean years between refreshes.