Adams County, Colorado Property Tax Appeal Guide (2026)

Adams County, Colorado property owners challenge their assessor's valuation first with the Assessor's Office directly, then with the county Board of Equalization (CBOE), and beyond that with the state Board of Assessment Appeals, district court, or binding arbitration. Colorado reassesses real property only in odd-numbered years, and Adams County's own assessor page confirms that 2026 is an intervening year, meaning only properties with a change in characteristics from the prior year (new construction, a permit, remodeling, a correction of previously omitted property, and similar changes) receive a new 2026 Notice of Valuation and a live appeal right this year. If you did not receive a 2026 Notice of Valuation, your property's value did not change and there is generally nothing to protest until the next reappraisal cycle in 2027.

How assessments work in Adams County

The county revalues real property every odd-numbered year using a data-collection period that runs up to June 30 of the year before the reappraisal year. For the 2025 reappraisal (whose values carry forward into 2026), that appraisal date was June 30, 2024. Once set, a property's actual value normally stays fixed through the following even-numbered intervening year, which is why most Adams County owners will not see a changed value or a new appeal window in 2026.

Assessed value, the number your mill levy is actually applied to, is calculated by multiplying actual value by a residential assessment rate. According to the Adams County Assessor's own published 2026 figures, residential and multi-family property uses a 6.8% assessment rate for local government levies and 7.05% for school levies, and the office notes these rates are set by the Colorado Legislature and are subject to change in the fall. Adams County spans many overlapping taxing districts, cities, school districts, water and fire districts, and special districts across Brighton, Thornton, Westminster, Commerce City, and unincorporated areas, so there is no single county-wide mill levy; the actual levy applied to any parcel depends on the specific combination of districts that serve that address, and owners should confirm their own parcel's levy through the Assessor's property search portal or their tax notice rather than assume a countywide number.

Whether you should appeal

Appeal if you received a 2026 Notice of Valuation and believe the value the Assessor assigned does not reflect what your property was actually worth as of the relevant appraisal date, or if the property's characteristics (square footage, condition, land classification) are recorded incorrectly. If you did not receive a 2026 notice, you generally have no active appeal this year; your value stayed the same as 2025 because Adams County, like the rest of Colorado, only reappraises broadly in odd years. Gather comparable sales from around the June 30, 2024 appraisal date, correct any factual errors in the county's property record (bedroom/bathroom count, square footage, lot size, condition), and be ready to show why the assigned actual value overstates market value.

Step-by-step how to file

The statutory protest window for real property value or classification appeals in Adams County runs May 1 through June 8; appeals postmarked after June 8 cannot be accepted, and if the deadline falls on a weekend or holiday it moves to the next business day. Appeals may be submitted by mail, email, fax, or in person to the Assessor's Office at 4430 South Adams County Parkway, Brighton, CO 80601 (phone 303-659-2120 or 800-824-7842, email assessor@adamscountyco.gov). If someone other than the property owner is filing, Adams County requires a notarized letter of authorization submitted with the initial appeal or the appeal will be rejected at the assessor level, since only the owner has legal standing to appeal. The Assessor's Office mails Notices of Determination on protests no later than August 15.

What happens after you file

If you disagree with the Assessor's Notice of Determination, the next step is the county Board of Equalization (CBOE). You have until September 15 to mail a completed CBOE appeal form to 4430 South Adams County Pkwy C5000A, Brighton, CO 80601, and CBOE hearings are held between September 1 and November 1. If you disagree with the CBOE's decision, Colorado law gives you three options, each with a filing deadline of not later than 30 days after the CBOE decision: appeal to the state Board of Assessment Appeals in Denver (303-864-7710), file in Adams County District Court in Brighton (303-659-1161), or pursue binding arbitration, for which the county commissioners maintain a list of qualified arbitrators. Each path has different costs, formality, and evidentiary rules, so review the option that fits your situation before the 30-day window closes.

If you missed the window

If you missed the May 1 to June 8 protest period and you have a genuine dispute over your value, your main remaining options are limited: watch for the next real reassessment cycle in 2027 to file during that protest window, or, if the issue is a factual error rather than a valuation dispute (for example incorrect square footage or a classification mistake), contact the Assessor's Office about a correction or an abatement/refund petition for a prior tax year, which follows a separate process from the annual protest. Adams County publishes an Abatement page through the Assessor's Office for exactly this kind of after-the-fact correction.

Local tips

Because 2026 is an intervening year for Adams County, most owners will see no new Notice of Valuation and have nothing to file this year; if you're unsure, check your parcel on the county's Property Search Portal or call the Assessor's Office directly. If you do have a 2026 notice, act early. Comparable sales evidence and correcting the county's factual property record (not simply asserting the number feels high) is what actually moves valuations at the informal and CBOE stages. Seniors 65 or older who have owned and occupied their home for at least 10 consecutive years, and veterans with a 100% permanent VA disability rating who have owned and occupied their home since January 1, can each apply for Colorado's homestead exemption, which exempts 50% of the first $200,000 of actual value; Adams County's deadlines are July 15 for the senior exemption and July 1 for the veteran exemption, both handled by the Assessor's Office.