Colorado Property Tax Assessment Rate, Mill Levies, and How to Protest Your Bill
Colorado's property tax system looks straightforward on the surface — there is an assessed value and there are mill levies. In practice, it is a layered structure involving state-mandated dual assessment rates, constitutional revenue limits, biennial reassessment cycles, and Metropolitan District mill levies that can double a property's annual tax burden. Understanding the mechanics is not optional for investors; it is the difference between an accurately modeled deal and one that fails on its first full-year tax bill.
How Colorado Property Taxes Are Calculated in 2026
Colorado uses a biennial reassessment cycle, with actual values updated in odd-numbered years based on comparable sales data from the preceding 18-month study period. The 2025 reassessment established values effective for the 2026 tax year.
Under the current system, Colorado applies two separate assessment rates to residential property, with different rates used for local government taxes versus school district taxes:
Local Government (county, municipality, special districts): Assessment rate of 6.8% applied to the property's actual value, after subtracting 10% of the actual value up to a maximum of $70,000. This subtraction is the legislative cushion from SB 24-233 and HB 24B-1001, designed to reduce residential property tax spikes from the post-Gallagher Amendment reassessments.
School Districts: Assessment rate of 7.05% applied directly to the full actual value, without the 10% subtraction.
Non-residential property: Commercial improved property is assessed at 25.0%, industrial/commercial other at 26.0%, and vacant land at 27.5% — all substantially higher than residential rates.
A Worked Example for a $500,000 Residential Property
Assume a local government mill levy of 40 mills and a school district mill levy of 35 mills:
Local government calculation:
- Value subtraction: 10% of $500,000 = $50,000 (under the $70,000 cap)
- Adjusted value: $500,000 - $50,000 = $450,000
- Assessed value: $450,000 × 6.8% = $30,600
- Local taxes: $30,600 × (40 ÷ 1,000) = $1,224
School district calculation:
- No subtraction applied; uses full actual value
- Assessed value: $500,000 × 7.05% = $35,250
- School taxes: $35,250 × (35 ÷ 1,000) = $1,234
Total annual property tax: $2,458
This is the base tax — before any Metropolitan District levy is applied.
Colorado Mill Levy Rates and Metropolitan Districts
A mill is one-thousandth of a dollar of assessed value. The total mill levy on any given property is the sum of all taxing entities that have jurisdiction over that parcel: the county, the municipality, school districts, fire districts, library districts, water districts, and any Metropolitan Districts.
In suburban Front Range communities built after 2000, Metropolitan District mill levies can add 30–50 mills on top of the standard county and school levies. On the same $500,000 property above, an additional 50 mills applied to the local government assessed value of $30,600 adds $1,530/year.
Over a $600,000 property in a mature Denver suburb with no metro district, the total annual property tax might run $3,000–$4,200. The same property in a newer master-planned community with an active metro district can run $5,000–$7,500/year — a difference that fundamentally changes the DSCR calculation on a financed deal.
Metropolitan Districts are legally authorized to increase their debt service mill levy up to the maximum cap defined in their service plan, which is frequently 40–50 mills, and in some cases higher if assessed valuations fall below projections. This escalation risk is why investors must check not just the current mill levy but the district's outstanding debt relative to its assessed valuation base.
Under House Bill 25-1219 (effective August 6, 2025), sellers of residential properties within metro districts established since 2000 must now disclose the specific annual tax dollar amount collected by the district, backed by a current county assessor tax certificate. This is a new protection — prior to this law, many buyers only discovered metro district taxes after the first full-year tax bill arrived.
How to find the mill levy: Pull the property's tax card from the county treasurer's online portal. Most Front Range counties (Denver, Adams, Arapahoe, Douglas, Jefferson, El Paso, Larimer, Weld) have publicly accessible property tax search tools that show the full mill levy breakdown by taxing entity. The county assessor's office website is the authoritative source.
Colorado Property Tax Protest: The Process
If you believe the county assessor has overvalued your property — particularly relevant after the 2025 biennial reassessment — you can formally protest the actual value determination. The protest window is strict: you must file between May 1 and June 8 of the assessment year (in odd-numbered reassessment years).
The protest process:
Gather comparable sales evidence. The assessor uses sales data from the 18-month study period ending June 30 of the preceding even-numbered year. Your protest should identify comparable sales in your specific neighborhood, of similar size, condition, and age, that sold at lower prices than your assessed value implies.
File the protest. Most Colorado counties now accept online protest submissions through the county assessor's portal. You will receive an acknowledgment and a scheduled hearing date with an appraiser.
Administrative hearing. Present your comparable sales analysis to the county assessor's appraiser. If the appraiser agrees, the value is adjusted at this stage. This is an informal process — most investors resolve protests here without legal representation.
Board of Assessment Appeals. If the administrative hearing does not produce a satisfactory result, you can appeal to the state Board of Assessment Appeals (BAA). This is a formal administrative proceeding. BAA hearings typically occur 8–18 months after submission.
District Court. If the BAA ruling is unsatisfactory, you can appeal to the Colorado District Court. This rarely happens for residential properties — the legal costs generally exceed any tax savings on a single property.
For investment property owners, a 5–10% reduction in assessed value on a $500,000 property reduces the taxable base by $25,000–$50,000. At a combined mill levy of 75 mills and a 6.8% residential rate, that translates to roughly $128–$255 in annual tax savings. Over a 5-year hold, the savings can justify the time cost of the protest process.
TABOR and the revenue cap context: Colorado's Taxpayer's Bill of Rights (TABOR), Article X, Section 20 of the state constitution, limits government revenue growth to inflation plus development growth unless voters approve an override. Many local taxing authorities have "debruced" — voted to remove the TABOR revenue cap — which means they can capture the full benefit of property value appreciation in their mill levy collections. Non-debruced districts are constrained, which can occasionally result in mill levy adjustments downward. Check whether your county's taxing entities have debruced; it affects the trajectory of your long-term carrying costs.
For a full model of how to underwrite Colorado property taxes for investment deals — including the metro district assessment methodology, DSCR impact calculations, and a worked example for suburban Front Range properties — the Colorado Investment Property Guide provides the framework investors use to build accurate carry-cost projections from day one.
Get Your Free Colorado Quick-Start Home Buying Checklist
Download the Colorado Quick-Start Home Buying Checklist — a printable guide with checklists, scripts, and action plans you can start using today.