Here’s a look at what’s changing – and what it means for Boulder property owners.
How property taxes are assessed in Boulder
Boulder County Property Taxes are based on two main components:
- The estimated value of your propertydetermined by the provincial assessor
- Mill taxeswhich are determined by Boulder County, the City of Boulder, school districts and other local taxing authorities
Your total tax bill is calculated by applying mill taxes to your assessed value. Even if mill taxes remain stable, taxes could still rise as property values rise.
Reassessment
Boulder County reassesses property values every two years. The most recent reassessment occurred in 2025, and those updated values will be used to calculate property taxes due in 2026.
For many homeowners, values remain higher than they were just a few years ago. As a result, even small changes in the factory levy can have a noticeable impact on tax bills.
Certified residential assessment rates for tax year 2025
For the 2025 tax year (payable in 2026), Colorado is using split residential property assessment rates because statewide property value growth remained below 5%.
This means that homes are assessed at different rates depending on which part of the tax bill is calculated:
- 6.25%: applies to the local government part (city, province, special districts)
- 7.05%: applies to the school district portion
These rates are set at the state level and apply uniformly throughout Colorado.
Changes in State Law: What’s Actually Different?
Recent State Legislation introduced two important concepts that affect the way taxes are calculated:
1. A value exclusion is applied first
Before assessment rates are applied, part of a property’s value is excluded from tax under the local government portion of the bill. This reduces the taxable value used for that portion only.
2. Split rates are applied separately
After the exclusion:
- The 6.25% rate is applied to the remaining value for local government taxes
- The 7.05% rate is applied separately for school district taxes, which do not receive the same exclusion
Because of this structure, homeowners still receive one tax bill, but it is calculated behind the scenes using multiple formulas.
It’s important to note: Even with exclusions and reduced rates, your final tax bill is still highly dependent on your property’s assessment and local mill taxes. If your assessed value has increased significantly, that increase may outweigh the relief measures.
Important dates homeowners need to know
If you own property in Boulder, keep these dates in mind:
- Valuation messages sent: First week of May 2025
- Deadline for appeal: June 9, 2025
- Tax assessments issued: January 2026
Payment options:
- Pay in full via April 30, 2026
- Or pay in two installments:
- First payment: March 2, 2026
- Second payment: June 15, 2026
What this means for homeowners in Boulder
For most homeowners, 2026 property taxes will reflect a combination of:
- Updated 2025 values, reassessed
- State-mandated value exclusions
- Split residential assessment rates
- Locally approved mill fees
Some property owners will see minimal changes, while others (particularly those with large appreciation increases) will notice higher tax bills despite the statewide relief efforts.
Understanding how these pieces fit together can help you plan ahead and avoid surprises when tax bills arrive.
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