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Duane Duggan, Realtor and Author, RE/MAX of Boulder
Duane Duggan, Realtor and Author, RE/MAX of Boulder

This May Day, one thing every property owner in Boulder County can depend on is receiving is a newly assessed property value. Since 2019 is an odd numbered year, state statute requires that every property in Boulder County be evaluated for “assessed value”. Notices of assessed value will go out countywide on May 1, 2019.  The new assessed value is based on past real estate market sales of comparable properties from July 1, 2016 to June 30, 2018.  If there isn’t enough information in that time frame, the assessor is allowed to go back five years to collect sales data. The assessor then uses a “time trending” appreciation rate by area to adjust values on the basis of when the sale occurred within the allowable time frame.  

The assessment and valuation process is an enormous task. In Boulder County, there are over 120,000 properties to assess by 45 employees of the Boulder County Assessor’s Office, of which most are Certified Appraisers.   

The valuation process includes the steps of discovery of properties; listing properties in the database; defining their characteristics; and categorizing properties as to how they are used, such as residential, commercial, or land. The data are then put through a statistical modeling process called mass appraisal.  The data from the sold properties are used to predict the values of the unsold properties using algorithms processed through statistical software. This advanced technology has helped the Assessor’s Office be much more accurate in determining values, without the benefit of personal visits to the interior of the property.

The assessment rate, which is assigned by the state legislature, is then applied to the property value and that determines the assessed value. For residential properties, assessed value currently stands at 7.2%, which was signed into law on June 5, 2017, changing from 7.96% of their actual value. For commercial properties and land, assessed value is 29% of the value.

Property taxes are then calculated by multiplying the assessed value by the mill levy of the particular area the property is located in. The goal of property value assessment is to equalize property values so property taxes are distributed fairly and equitably between property owners.

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. However, it is important to point out that the Assessor’s Offices does not set or collect taxes, it only provides the value assessment.

During the recession, values didn’t rise much. Since 2012, however, values have risen sharply in Boulder County, causing many property owners to have questions about their property’s assessed value. The Assessor’s Office strives to be accurate, but the process is still a mass appraisal platform. Whenever a property owner has questions about the value, they can visit or call the Assessor’s Office or respond through the Boulder County Assessor’s website.

It’s important to understand that there is a formula for determining the actual amount of taxes. The assessment is part of the process, but the mill levy that is applied to the assessment is actually what determines the taxes. Sometimes property owners may argue very hard for a small amount of value, but when the whole formula is applied, taxes may not change that much. 

If a property owner disagrees with the assessed value, appeals must be filed by the end of the first day in June. Property owners will be notified of the ruling on the last day of August when the Assessor’s Office mails out the Notice of Determination. If a property owner still doesn’t agree, an appeal can be filed with the County Board of Equalization.

You can contact the Boulder County Assessor’s Office by phone at 303-441-3530 or visit 1325 Pearl, Boulder. You can also visit the website at

By Duane Duggan, RE/MAX of Boulder. Duane has been a Realtor for RE/MAX of Boulder in Colorado since 1982 and has facilitated over 2,500 transactions over his career, the vast majority from repeat and referred clients. He has been awarded two of the highest honors bestowed by RE/MAX International: The Lifetime Achievement Award and the Circle of Legends Award. Living the life of a Realtor and being immersed in real estate led to the inception of his book, Realtor for Life. For questions, e-mail Duane at, call 303.441.5611 or visit