Assessment & Valuation

Property Assessment Overview

Why Property Is Assessed

The property assessment process is the basis for generating property tax revenues that pay for schools, roads, fire protection, police protection, and other local services.

All revenue from property taxes are distributed to taxing entities with in Boulder County. Property tax revenue does not support any state services.

The Assessor’s Role

The Boulder County Assessor identifies and values all property within Boulder County in accordance with state law. The goal is to equalize property values so taxes are distributed fairly and equitably between property owners.

State Mandate for the Valuation of Properties

State statute requires that each property in the county be re-valued by the County Assessor in odd numbered years.

The value is based on real estate market activity during the 18 month data collection period that runs from January 1 of the previous odd numbered year to June 30 of the most recent even numbered year.

If there is not enough real estate market data collected during the 18 month, odd-numbered year period, the Assessor can use data collected back five years from June 30 of the most recent even-numbered year. Our office typically finds the optimum number of sales are derived from a 24 month period.

Determining Property Value

The Assessor’s Office uses the following methods to determine property value:

  • Evaluation of real market data that reflect actual sales in the marketplace
  • Comparison of properties of “like” characteristics and location using state-of-the-art modeling software and advanced mass property appraisal tools
  • Incorporation of information derived from property appeals

Factors in Comparing Like Properties

The most central factors that evaluators use for property valuation are:

  • Location
  • Living Area
  • Finished Basement
  • Age
  • Baths

Uniform Assessments

After properties have been appraised, the values are analyzed to ensure accurate and equitable assessments. Colorado law requires all Assessors to value property at a specific level and within certain uniformity standards. This provides equity in distribution of state school funding, local tax burden, and assessments that cross county lines.

An independent auditor conducts an annual 1% study of all property in each county. Findings are reported to the State Board of Equalization each year.

Certification to Taxing Authorities

The Assessor certifies, each year in August, the total assessed value of all properties within the boundaries of each Taxing Authority.

  • For non-residential properties, assessed values are calculated by multiplying the actual value by 29%.
  • For residential properties, the assessment percentage is subject to change by the Colorado Legislature each odd-numbered year. The change in percentage is intended to balance the tax burden between residential and all other properties. For the current appraisal period, the residential assessment rate is 7.2% (signed into law June 5, 2017, changing from 7.96%).

Taxing Authorities use these figures to determine their mill levies. If there is any change in the assessed value due to Board of Assessment Appeal decisions, abatements or any other reason, the values are re-certified to the affected Taxing Authorities in early December.

Assessments & Taxes

See How Property Taxes Are Calculated for further information on determining mill levies and figuring property taxes.

Taxpayer Rights & Responsibilities

Property owners and taxpayers have specific rights, remedies, and responsibilities in the assessment process:

  • You have the right to examine the Assessor’s property records.
  • If you disagree with your property value, you may file an appeal with the Assessor.
  • You have the responsibility to provide accurate information to the Assessor about property you own.
  • You have the responsibility to participate in budget hearings held by school boards, cities and towns, and special districts that levy taxes on your property.

Contact Us


Phone: 303-441-3530
Fax: 303-441-4996

Business Personal Property
Phone: 303-441-3316
Fax: 303-441-1783

Mailing Address
Main: PO Box 471
Boulder, CO 80306-0471



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