Arapahoe County, CO Property Tax Appeals, Rates & Due Dates

Arapahoe County homeowners who disagree with their assessor's value must protest in writing (or in person) to the Arapahoe County Assessor's Office, not the Treasurer. The real-property protest window runs each year from May 1 through early June — for tax year 2026 the deadline was June 8 — and it resets annually, so check the Assessor's website each spring for the exact current-year date. Missing this window generally forfeits your right to challenge that year's value.

The Two-Year Reassessment Cycle

Colorado reassesses real property on a two-year cycle, with new values published in odd-numbered years (2025, 2027, 2029...). Personal property, by contrast, is revalued every year. In the "off" even year, your assessed value normally carries over unchanged from the prior odd-year reappraisal unless something specific changed (new construction, a remodel, a correction, or an appeal).

The value the Assessor sets is not based on today's market — it is anchored to a fixed data-collection window that closes well before the notice is mailed. For the 2025–2026 reappraisal cycle, the Assessor was required to use qualified sales from January 1, 2023 through June 30, 2024 (an 18-month window), with older sales data (back up to five years) pulled in only if there weren't enough qualifying sales in that window. This is precisely why a Notice of Valuation can feel out of step with what homes are actually selling for the month you receive it — the number reflects a market snapshot that is already a year or more old. The next reappraisal cycle (2027–2028) will use a comparable 18-month sales window ending in 2026, under the same mechanism; the exact cut-off dates for that cycle had not yet been published by the state as of this writing.

Protest, Then Appeal: Colorado's Terminology Ladder

Colorado's process uses two different words for two different stages, and mixing them up is the most common homeowner mistake:

1. Protest — Your first step is a protest filed directly with the Arapahoe County Assessor, either in writing or by presenting oral objections. This must be filed within the annual window described above (opens May 1; deadline in early June, subject to the Assessor's published schedule).
2. Notice of Determination — The Assessor reviews your protest and mails a written decision.
3. Appeal to the County Board of Equalization (CBOE) — If you disagree with the Assessor's determination, you may appeal to the Arapahoe County Board of Equalization. The CBOE must notify you in writing within five business days of its decision.
4. Board of Assessment Appeals, District Court, or Binding Arbitration — If you're still dissatisfied after the CBOE ruling, you have 30 days from the date the CBOE decision was mailed to pursue exactly one of three paths: a de novo hearing before the Colorado Board of Assessment Appeals, a de novo case in Arapahoe County District Court (filing fee required), or binding arbitration (a refundable deposit of $150 for residential property is required, and the arbitrator's ruling is final and cannot be further appealed).

Because Arapahoe County's population exceeds 300,000, the state allows — and Arapahoe uses — an "alternate" protest and appeal schedule that shifts when the CBOE holds hearings and issues its own responses later in the summer than the state's baseline schedule for smaller counties. The taxpayer-facing protest deadline itself is not affected by this; only the county's internal CBOE processing calendar shifts.

Residential Assessment Rate

Colorado does not tax your home's full market value — it applies a statutory assessment rate to your actual (market) value to produce an "assessed value," and that assessed value is what tax rates are multiplied against. This rate has changed several times in recent years through a mix of ballot measures and legislation, so a figure remembered from a prior year may already be wrong.

For tax years 2025 and 2026, Colorado uses two different residential assessment rates depending on which taxing authority is calculating its share:

• 6.8% for local governments (county, city, special districts, etc.)
• 7.05% for school districts

So a home with a $275,000 actual value produces an assessed value of about $18,700 for local-government tax purposes and about $19,388 for school tax purposes — two separate assessed values feeding two separate calculations that are then added together on your bill. Confirm the current year's rates before relying on them, since the legislature has adjusted residential assessment rates multiple times in the last several years.

Mill Levies: Many Taxing Authorities, One Bill

Arapahoe County itself is only one of several overlapping "taxing authorities" that set a rate against your assessed value — cities, school districts, water and sanitation districts, and other special districts each set their own rate, usually expressed in mills (a mill is $1 of tax per $1,000 of assessed value). Your total tax rate is the sum of every authority's levy that applies to your specific property location. Two homes with identical values a few blocks apart can owe noticeably different amounts if they sit in different city limits or different special-district boundaries. Because your protest only challenges the value the Assessor assigned — not the mill levies set independently by each taxing authority — a successful protest lowers your bill by reducing the base the levies are applied to, not by changing the levies themselves.

When Property Taxes Are Actually Due

This is a completely different deadline from the protest window above, and confusing the two is a common costly mistake. Arapahoe County property tax bills, covering the preceding year, are mailed after January 1. You then have two payment options:

• Two half payments: the first half is due by the last day of February, and the second half is due by June 15.
• One full payment: due by April 30 (this is also the only option if your total bill is $25 or less).

Paying late doesn't create any new right to protest that year's value — protest rights are governed entirely by the May–June window described above, months before these payment deadlines even arrive.

Exemptions That Can Reduce Your Bill

Two Colorado exemptions are commonly available to Arapahoe County homeowners, and both require an affirmative application — they are not automatic:

• Senior Property Tax Exemption: Available if at least one owner is 65 or older as of January 1 and has occupied the home as a primary residence for at least 10 consecutive years prior to that date. Qualifying seniors get 50% of the first $200,000 of actual value exempted from property tax. Applications open January 1 and are due on or before July 15 of the year the exemption is requested.
• Disabled Veteran Property Tax Exemption: Qualifying disabled veterans receive the same 50% exemption on the first $200,000 of actual value for their primary residence. Applications go to the Colorado Department of Military and Veterans Affairs, Division of Veterans Affairs, and are due by July 1 of the year requested. Eligibility criteria are set by the state — confirm your qualification with the Division of Veterans Affairs before applying.

Neither exemption changes the deadline to protest your property's value; they're separate programs you can pursue in the same year as a protest.

Look Up Your Property Record

Before protesting, pull your own property record to see exactly what the Assessor has on file — classification, characteristics, and the actual value for both the prior and current years. Arapahoe County's official property search tool is available at the Assessor's Office website: arapahoeco.gov under County Departments → Assessor → Property Search. The same page links to the county's GIS mapping tool (ArapaMAP) and to interactive dashboards showing recent residential sales and year-over-year value changes by neighborhood, which are useful for gathering comparable-sales evidence before you file a protest.

Grove Hopper does not file appeals on your behalf and is not a law firm; this guide is informational only. Always confirm current-year deadlines, rates, and forms directly with the Arapahoe County Assessor's Office before acting.