Colorado Property Tax Deadlines
Colorado’s calendar runs a full season ahead of the bill: the value notice and the entire protest-and-appeal sequence happen in spring and summer, the levies are set in the fall, and the bill arrives after January 1 of the next year. The calendar also runs on two parallel schedules — the standard one and the alternate schedule that large counties must use — so confirming which schedule your county is on is the first step of any Colorado deadline check.
By May 1: the Notice of Valuation
Real property Notices of Valuation are mailed by May 1 of each year. The notice lists the location, classification, value-relevant characteristics, and the actual value for the prior and current years. Statutory dates shift for weekends and holidays — the date printed on the notice and the assessor's published dates are the ones to rely on.
Date: By May 1 (annual mailing; real property revalued in odd years)
May 1 – June 8: the protest window
An owner who disagrees with the actual value or classification presents oral or written objections to the county assessor during the protest period, May 1 through June 8 for real property. Counties with populations over 300,000 are required to use an alternate schedule, and any county may elect it — check the assessor's published dates.
Anchor: the May 1 notice mailing window · Basis: rule tied to an event
The Notice of Determination and the county board
The assessor must decide the protest and mail a Notice of Determination. Standard schedule: the county board of equalization sits from July 1 and must conclude hearings and decide by August 5, notifying the owner in writing within five business days. Alternate schedule (large counties): NOD by August 15, hearings from September 1, responses by November 1.
Anchor: the protest period; schedule depends on county population · Basis: rule tied to an event
30 days: arbitration, district court, or the BAA
A county board of equalization decision can be appealed to an arbitrator, the district court, or the state Board of Assessment Appeals within 30 days of the date the decision was mailed.
Anchor: the CBOE decision's mailing date · Basis: rule tied to an event
The payment dates
Tax bills reflecting the prior year's taxes are mailed as soon as possible after January 1. Amounts above $25 may be paid in one payment by April 30 or in two equal halves — the first due by the last day of February, the second by June 15. Amounts of $25 or less are due in full by April 30.
Date: February 28/29 (first half) · April 30 (full or ≤$25) · June 15 (second half)
The shape of a year (illustrative, standard schedule)
Illustrative sequence for a revaluation year on the standard schedule — your assessor’s published dates control, and statutory dates shift for weekends and holidays.
- January 1: the assessment date — classification by actual use.
- By May 1: the Notice of Valuation arrives, showing prior and current actual value.
- May 1 – June 8: the protest window with the assessor — oral or written.
- Late June: the Notice of Determination arrives; the CBOE appeal window opens from its mailing.
- July 1 – August 5: county board hearings and decisions, with written notice within five business days.
- Within 30 days of the board’s mailed decision: petition to arbitration, district court, or the Board of Assessment Appeals.
- Fall: taxing authorities set the mill levies (school districts levied separately).
- After January 1: tax bills mailed; one payment by April 30, or half by the last day of February and half by June 15.
What this tells you: the Colorado appeal year is effectively over by September — everything after that (levies, bills, payments) is arithmetic on the value the process fixed. Owners who wait for the bill to decide whether to appeal are a full cycle late.
What it does not tell you: whether your county is on the alternate schedule (mandatory over 300,000 population, elective otherwise), and the adjusted dates for weekends and holidays — both published by your assessor.
Where the processes are explained
- Actual value and the assessment rate — the chain that builds the tax.
- The Notice of Valuation explained — the two values and the sales-study window.
- Protesting and the appeal path — the ladder and the three routes beyond the county board.
Sources
- Colorado Division of Property Taxation, Department of Local Affairs (State of Colorado) — Understanding Property Taxes in Colorado
- Colorado Division of Property Taxation, Department of Local Affairs (State of Colorado) — Protests and Appeals
- Colorado Division of Property Taxation, Department of Local Affairs (State of Colorado) — Property Tax Map (statewide taxing districts and rates)