Bill Spencer  

Bill Spencer

Benton County Assessor

Welcome to the Benton County Assessor’s Home Page

As your Benton County Assessor, I hope you find the information on our web site most helpful.  The goal of this web site is to help you find the information you need and to keep our “search for property” information open 24 hours a day, 7 days a week.

Property Search   


Treasurer's Office  .

Mission Statement
Our mission is to administer a property assessment system, which meets constitutional and statutory requirements, in an efficient and professional manner, while striving to provide courteous and excellent service to our customers The Benton County Assessor’s Office is responsible for determining the value of all taxable real and personal property in the County, set on a foundation that those determinations are fair and understandable.  This is done in accordance with Washington State law, which requires that all properties are assessed at 100% of fair market value.  In addition, the Assessor’s Office manages accessible property information, provides timely and accurate assessments for tax purposes, and maintains a detailed parcel map of all parcels within the County.
Role of the Assessor’s Office
Appraise and add all real and personal property new construction valuations to the tax base. Preserve and provide accurate property ownership, parcel database and cadastral mapping for all property. 


Assessor’s Database Management                                                                                                                         

Retain accurate property ownership/taxpayer, parcel inventory data, taxing district boundary definitions, land use definition, assessed valuation data, and mapping for all properties and accounts.                                                                                                                                                           

New Construction Valuation                                                                                                                      

Inspects and determines value of new construction.                                                                                                             

Personal Property Valuation                                                                                                                      

Businesses must report their equipment and asset listings annually. These are valued at 100% assessed value to market value.                                                                                                                    

Public Assistance                                                                                                                             

Provide information, education, and assistance to public inquiries by phone and at our physical office.  Daily updates of record changes assist our website to be current for our website users.                                                                             

Real Property Revaluation                                                                                                                          

Physically inspect and statistically revalues real property parcels on an annual basis, to maintain a 100% assessed value to market value relationship.                                                                                                                                       

Tax Roll Processing                                                                                                                         

Process assessment roll to certification as a Property Tax receivable collection roll for the Treasurer’s billing, collection and distribution. Report and audit verification are required by statute, and accurate calculations and distributions must be provided.                                

Valuation Defense                                                                                                                         

Answers to valuation and procedures before a distinct and separate administrative appeals mechanism.                           
  • Contacts
    Who to contact within the office for the department you need.
  • FAQ's
    Frequently asked questions about the Assessor's Office.
  • Forms
    Various forms for applications such as tax relief programs.
  • Office of the Assessor
    Duties and responsibilities assessed values for property tax purposes.
  • Personal Property
    Which types of personal property are taxable and required to report?
  • Real Property
    There are various real property categories found in Benton County
  • Tax Booklet
    Annual levy rate information and distribution.
  • Tax Relief
    Various programs for relieving or reducing property tax obligations. 
  • Valuation Appeal Forms
    Information about how and when to appeal your valuation.

8:00 a.m to 5:00 p.m.
Monday through Friday
(excluding holidays)

Prosser Courthouse

Second Floor
620 Market St
Prosser, WA 99350
Phone      (509) 786-2046

Fax          (509) 786-5657
Toll Free  (509) 736-3088

Benton County    620 Market Street    Prosser, Washington 99350
Phone: (509) 786-5710 or (509) 783-1310
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