Property Tax Calculation

How Property Taxes Are Calculated

Actual Value, Assessment Rate, and Mill Levy

Assessment Rate

The Assessment Rate below reflects rates for the 2024 tax year that impacted tax bills paid in 2025. For tax year 2025 that will impact taxes paid in 2026, the residential assessment rates have not yet been finalized. We will update this page when we hear the final rates from the State. For more information on the 2025 assessment rates, please visit the Division of Property Taxation’s Assessment Rates web page.

Type of Property2024 Assessment Rate2024 Value Adjustment2025 Assessment Rate2025 Value Adjustment
Multi-Family housing: Duplex/Triplex, 4-8 unit Apartments, 9+Unit Apartments6.7%-$55,000TBD$0
All other residential property: Single family, Condominiums, Townhomes6.7%-$55,000TBD$0

Type of Property2024 Assessment Rate2024 Value Adjustment2025 Assessment Rate2025 Value Adjustment
Lodging27.9%-$30,00027%$0
Renewable Energy26.4%-$30,00027%$0
Agricultural26.4%N/A27%$0
Vacant Land27.9%$027%$0
Commercial27.9%-$30,00027%$0
Industrial27.9%$027%$0
Oil & Gas production87.5%$087.5%$0

Property Tax Calculations

2023/2024 Property Tax Calculation

For tax years 2023/2024 (taxes paid in 2024/2025), there is an additional component for some properties. In 2022, the Colorado Legislature passed SB22-238 which reduced assessment rates and also provided a one time value adjustment to residential ($15,000 adjustment) and commercial properties ($30,000 adjustment) for tax year 2023.

In November 2023, the Colorado Legislature held a special session and passed SB23B-001. This bill increased the residential reduction from $15,000 to $55,000 and lowered the residential assessment rate from 6.765% to 6.7%. The original reductions for commercial properties from SB22-238 remain.

In 2024, Colorado Legislature passed HB24B-1001, which makes many changes to how taxes are calculated starting for tax year 2025 (taxes paid in 2026). It also extended the assessment rates and $55,000/$30,000 value adjustments from tax year 2023 into tax year 2024. Therefore, the assessment rates and value adjustments are the same for tax years 2023 and 2024.

Properties that fall into these categories will have the value adjustment applied to their Actual Value before multiplying by the assessment rate. For example:

(
Actual
Value
–
Value
Adjustment)

X
Assessment
Rate
=
Assessed
Value

and then

Assessed
Value
X
Mill
Levy
=
Taxes
Due


The example below is for a residential property with an Actual Value of $450,000 for tax year 2024, paid in 2025, with a Value Adjustment of $55,000, an Assessment Rate of 6.7%, and a Mill Levy of 92, there will be $2,435 in taxes due.

(
$450,000
–
$55,000
)

X
6.7%
(or 0.067)
=
$26,465

and then

$26,465
X
92
(or 92 Mills
or 0.092)
=
$2,435

2025 Property Tax Calculation

Beginning in tax year 2025 (payable in 2026), there are two assessment rates; one for school districts and one for all other local government districts (fire districts, cities, etc.). For more information on the 2025 property tax calculation, please visit the Understanding Property Taxes in Colorado web page.
School Districts Calculation

Actual
Value
X
Schools
Assessment
Rate
=
Schools
Assessed
Value

and then

Schools
Assessed
Value
X
Schools
Mill
Levy
=
Schools
Taxes
Due


Other Government Districts Calculation

Actual
Value
X
Other
Assessment
Rate
=
Other
Assessed
Value

and then

Other
Assessed
Value
X
Other
Mill
Levy
=
Other
Taxes
Due


Property Tax Calculation Total

School
Taxes
Due
+
Other
Taxes
Due
=
Total
Taxes
Due

The example below is for a residential property with an Actual Value of $800,000 for tax year 2025, paid in 2026, with an assumed Residential Assessment Rate of 7.05% for school districts, and 6.25% for local government. The school district’s Mill Levy is 30, and for all other local government districts that serve this property, the total Mill Levy is 65. The taxes would be calculated as follows:
School Districts Example

$800,000
X
7.05%
(or 0.0705)
=
$56,400

and then

$56,400
X
30
(or 30 Mills
or 0.03)
=
$1,692


Other Government Districts Example

$800,000
X
6.25%
(or 0.0625)
=
$50,000

and then

$50,000
X
65
(or 65 Mills
or 0.065)
=
$3,250


Property Tax Calculation Total

$1,692
+
$3,250
=
$4,942

Additional details on the Mill Levy are below. Seniors and disabled veterans may qualify for certain property tax exemptions that could impact their final tax amount.

Much more information on property taxes, including Property Tax Search, due dates, and paying taxes online, is available on the Boulder County Treasurer page.

Tax Rate or Mill Levy

The Tax Rate and Mill Levy are two different ways of expressing the same information. The Tax Rate is expressed as a percentage, while the Mill Levy is expressed in mills (1 mill = $1 of property tax for every $1,000 of assessed value)

Generally, properties are affected by several taxing entities. Each taxing entity determines what revenues will be required to operate during the coming fiscal year. The required revenues are then divided by the total assessed value to determine the tax rate/mill levy for each entity. To determine the total tax rate for a property, add the tax rates for each entity that impacts a property.

Mill Levy Example:

  • The assessor determines the total assessed value for properties within a school district’s boundaries as $100,000,000.
  • The school board of that school district determines the budgeted property tax revenues needed are $1,398,000.
  • $1,398,000 (tax revenue) divided by $100,000,000 (assessed value) = 1.3980% Tax Rate, or 13.98 Mills (Mill Levy), for that district’s portion of the total Mill Levy.
  • The school district’s tax rate is $13.98 in revenue needed for each $1,000 of assessed value.

Assessor Links

Contact Us

Assessor

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

Email

Mailing Address

PO Box 471
Boulder, CO 80306-0471

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

Locations

Assessor Boulder and Longmont Drop Boxes

Boulder

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

Longmont

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

Lafayette

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

Website

BoulderCountyAssessor.gov

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