Assessment & Valuation

Real Property Assessment & Valuation


State law requires that all real property (land and buildings) in a county be revalued (reappraised) every odd-numbered year. The goal is to equalize property values, so taxes are distributed fairly and equitably between all property owners.

A 24-month base period is used for property assessment, and the official appraisal date is June 30 of the year prior to the reappraisal year. As an example, for the current 2023/2024 tax year, the base appraisal period was July 1, 2020 – June 30, 2022; and June 30, 2022 was the official appraisal date.

After properties have been appraised, the values are analyzed to ensure the assessments are accurate and equitable, and meet state-mandated uniformity standards.

Determining Property Value

The Assessor’s Office evaluates data from actual sales in the marketplace, uses state-of-the-art modeling software and advanced mass property appraisal tools to compare properties of similar characteristics and location, and incorporates information from property appeals to determine a property’s value. Additional details are available on the Property Valuation Process page.

The results are analyzed to ensure accurate, uniform, and equitable assessments. An independent auditor hired by the State of Colorado also conducts an annual study of 1% of all properties in each county, and these findings are reported to the State Board of Equalization.

Assessment & Taxes

Property assessment is the basis for generating tax revenues that are collected by the Treasurer to pay for schools, roads, fire protection, police protection, and other local services. Every August the Assessor certifies the total assessed value of all properties within the boundaries of each local taxing authority. All property tax revenues are distributed to taxing entities within Boulder County and do not support any state services. See links in the sidebar on How Property Taxes Are Calculated, Mill Levies & Taxing Districts, and Property Tax Calculation for more information.

Contact Us


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


Mailing Address

PO Box 471
Boulder, CO 80306-0471

Hours: 7:30 a.m. to 5 p.m.
Closed Friday


Assessor Boulder and Longmont Drop Boxes


1325 Pearl St., 2nd floor
Boulder, CO 80302
Hours: 7:30 a.m. to 5 p.m.
Map and Directions Boulder Location


515 Coffman St., Suite 114
Hours: 7:30 a.m. to 5 p.m.
Monday only
Map and Directions Longmont Location


1755 S Public Road
Hours: 7:30 a.m. to 5 p.m.
Tuesday only
Map and Directions Lafayette Location