Travis Bunn

Founder, AppealDesk · Published February 28, 2026 · Updated August 21, 2026

Colorado Property Tax Appeal Deadline 2026: June 8, Statewide

Updated August 2026

Colorado has one protest deadline, and it is the same in every county: your objection to the assessor must be postmarked or delivered by June 8. The window opens May 1, when Notices of Valuation go out. If you have seen pages claiming some counties use May 1 and others June 15, that split does not exist in Colorado law; the dates that matter are May 1 (window opens), June 8 (protest deadline), and then September 15 if you take a denial to the county board.

The Real Colorado Timeline (C.R.S. 39-5-122)

• May 1: Notices of Valuation mailed; the protest window opens
• June 8: Your objection must be postmarked or delivered to the county assessor
• By about August 15: The assessor mails a Notice of Determination on your protest
• September 15: Deadline to appeal a denial (or a missing determination) to the County Board of Equalization
• After the CBOE: Binding arbitration, the state Board of Assessment Appeals, or district court

Reading this in late August 2026? The June 8 protest deadline has passed, but if you protested and were denied, your Notice of Determination arrived around mid-August and your County Board of Equalization appeal is due September 15. That clock is running right now.

Missed June 8? The Abatement Path

A missed protest deadline in Colorado is not the end of the road. If you did not object by June 8, you can petition for an abatement or refund under C.R.S. 39-10-114 after the taxes are levied, by contacting your county assessor. It is a slower path and it starts after the bill exists rather than before, but it is the legislature's own second chance for owners who missed the protest window, and it can reach back to correct an erroneous valuation.

Colorado's Appeal Levels

Level 1: County Assessor (protest by June 8)

• Free to file, online, by mail, or in person in most counties
• Many protests resolve here
• Decision comes as a Notice of Determination by ~August 15

Level 2: County Board of Equalization (by September 15)

• Written appeal of the assessor's determination
• Formal hearing before the board
• Independent review of your evidence

Level 3: After the CBOE

• Binding arbitration, the Board of Assessment Appeals, or district court
• Costs rise at each level
• Most homeowner cases are decided at levels 1 and 2

One Colorado Trap Worth Knowing: The Evidence Window

Colorado values property from a statutory base period, not from whatever sold last month. Sales that closed after the base period ends can be dismissed no matter how similar the homes are. Before you lean on a recent sale, confirm it falls inside the period your county's notice cites; boards deny otherwise-good cases on this point.

Evidence That Wins in Colorado

For Residential Properties:

1. Comparable sales from the statutory data period - The single most persuasive evidence
2. Condition issues - Snow damage, altitude wear, deferred maintenance
3. Lot challenges - Slope, access, utilities
4. Professional appraisal - Worth it for big gaps

Colorado-Specific Factors:

• Wildfire risk zones and insurance availability
• Water rights status
• Short-term rental restrictions
• Conservation easements

Mountain Property Challenges:

• Seasonal access only
• Propane/septic costs
• Internet limitations
• Snow removal burdens

Front Range vs Mountain Strategies

Denver Metro Appeals

• Plenty of comparables to choose from
• Data-driven arguments work
• Condition adjustments matter

Mountain Counties

• Limited comparables
• Seasonal factors weigh heavily
• Access issues common
• Local knowledge helps

Western Slope

• Energy boom/bust impacts
• Water rights critical
• Agricultural considerations

Eastern Plains

• Agricultural use is the key question
• Oil/gas impacts
• Lower overall values

Common Colorado Problems

Problem #1: Wildfire Risk Ignored

• Insurance costs rising sharply in exposed areas
• Some areas hard to insure at all
• Mitigation expenses high

Solution: Document insurance quotes and cancellations

Problem #2: Water Rights Confusion

• A large value component
• Often assessed wrong
• Well vs municipal matters

Solution: Prove your actual water situation

Problem #3: STR Restriction Impact

• Some towns restrict short-term rentals
• Assessment can assume a use the ordinance no longer allows

Solution: Show the ordinance change and its value impact

Special Colorado Considerations

Senior Property Tax Exemption

• Must be 65+ and meet the long-term occupancy requirement
• Exempts a share of your home's value
• Filed separately from an appeal, and can be combined with one

Disabled Veteran Exemption

• Separate application through the state
• Surviving spouses may be eligible
• Combine with an appeal on the remaining value

Property Tax Deferral

• Programs for seniors and other qualifying owners
• The state pays and takes a lien; interest accrues
• A cash-flow tool, not a reduction; consider it separately from an appeal

Agricultural Classifications

• Significant reductions when land qualifies
• Separate application
• Then appeal the remaining value if still too high

Your Action Plan

The Dates:

1. May 1 - Notice of Valuation arrives; window opens
2. June 8 - Protest postmarked or delivered to the assessor
3. September 15 - CBOE appeal if the assessor said no

Universal Steps:

1. Read your Notice of Valuation - Compare it to reality
2. Check the data period - Only in-period sales count
3. Document everything - Photos, costs, issues
4. File early - Do not ride the postmark
5. Follow through - CBOE by September 15 if denied

The Bottom Line

Colorado's protest deadline is June 8, statewide, no county exceptions. The window opens May 1, the assessor answers by mid-August, and a denial can go to your County Board of Equalization until September 15. Miss June 8 and the abatement petition is the honest fallback.

With Colorado's wildfire, water, and mountain-access complexities, successful appeals come down to in-period comparable sales and documented property facts. Know the three dates, and build the evidence before the window opens.

Statutory basis: C.R.S. 39-5-122 (protest to the assessor by June 8), C.R.S. 39-10-114 (abatement petitions). Confirm hearing logistics and filing methods with your county assessor.