General Tax Assessment Information

Residential Property
The County is responsible for appraising all urban and rural residential properties.  A mass appraisal method is used to appraise all residential properties following the rules and procedures in the Department of Revenue's publication, Appraisal Methods Manual.  In addition, we use cost factor books published by the Department of Revenue to determine the base cost of structures; Cost Factors for Residential BuildingsCost Factors for Manufactured Structures, and Cost Factors for Farm Buildings.  All residential properties within Columbia County are recalculated annually using the current inventory data in our system.

Recalculation requires an annual setup of land values, local cost factors, and depreciation schedule for each area that has sufficient data entered in the system.  Values are then electronically recalculated using the new factors without a physical inspection.  These setups are completed using sales data prior to the assessment date of January 1, so an additional market trend study is done later to further adjust the recalculated value based on the actual market.  Areas that are not yet able to be recalculated have only a market trend study completed to adjust the previous year's value to the current year.  The most recent summary of the analysis and conclusions is available for download on our Forms and Publications page.

Commercial and Industrial Property

The County is responsible for appraising all commercial and small industrial properties.  The Department of Revenue, Property Tax Division, Valuation Section is responsible for appraising all specialized improved industrial properties valued at more than $1,000,000.


Commercial and industrial properties are often appraised based on the cost approach using Marshall & Swift Valuation Service cost factors due to the difficulty in obtaining rent and income data, although all three approaches to value (income, market, and cost) are considered when determining the final value. 


Industrial properties with unique structures, machinery, and equipment are required to file a Real Property Return and Personal Property Return if valued by the county, or an Industrial Property Return if valued by the Department of Revenue.  These forms are required to be filed annually between January 1 and March 15.

Business and Floating Personal Property

Confidential Personal Property Returns are mailed to all business and floating property owners within Columbia County at the beginning of January.  These forms are to be completed and mailed back to us by March 15.  If you do not receive a return, it is your responsibility to request or download a form, and to ensure it is filed timely. 


For more information on Personal Property or to download a form, see the Oregon Department of Revenue Website on Personal Property Assessment and Taxation.

Manufactured Dwellings

Manufactured dwelling ownership and siting information is maintained by the Building Codes Division (BCD) of the Oregon Department of Consumer and Business Services (DCBS). 


The Columbia County Assessor's Office can process applications for manufactured home ownership or situs changes as an agent for the Building Codes Division.  The cost for ownership and situs changes is $55 per application.  The cost for trip permits is $5 per section. We will continue to provide certification that taxes have been paid for those who choose to process the change online through the Building Codes Division of the Oregon Department of Business and Consumer Services website.  Please visit for more information.


For changes requested after July 1 and prior to tax certification for the current tax year, an estimated tax for the current tax year will be collected.


CERTIFICATE OF TAXES PAID ON MANUFACTURED STRUCTURE can be downloaded here, and you may bring or mail the form to our office or email to for completion.


Additional forms can be downloaded from BCD.

Property Records Online

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Phone Numbers
Fax: 503-397-5153
Emergencies: Dial 911
230 Strand St.
Columbia County Courthouse Annex
St. Helens,

Monday - Friday
8:30 a.m. to 5:00 p.m.