Colorado Property Tax Guide 2026: How Your Bill Is Set

Your bill comes from three numbers — and only one is set by your county.

Colorado property taxes are calculated in arrears, which means the bill that lands in January pays for the year that just ended. The formula is simple on paper:

Actual value × assessment rate = assessed value. Assessed value × mill levy = your tax bill.

Actual value is what the county assessor says your property is worth — an estimate of market value, not a number you negotiate with anyone. The assessment rate is the percentage of that value that is actually taxable, and it is set by the state legislature, not by your county. For 2026, residential property uses two rates: 6.8% for local-government levies (applied after a value exclusion described below) and 7.05% for school-district levies. The resulting assessed value is the slice of your home's value that gets taxed.

Mill levies are set by the taxing authorities themselves — the county, the city, the school district, fire districts, metro districts, library districts, and every other local body that bills you. One mill is one dollar of tax for every $1,000 of assessed value. Your county assessor does not set mill levies; voters and district boards do. The county treasurer sends the bill and collects it.

Nobody in the process can move your tax bill alone. The assessor sets the value, the legislature sets the rate, and local districts set the levies.

For a hypothetical $500,000 home in tax year 2026:

$30,600Local-government assessed value: ($500,000 − $50,000 exclusion) × 6.8%

$35,250School-district assessed value: $500,000 × 7.05%, no exclusion

$2,448Tax to local governments at a hypothetical 80 mills

$1,939Tax to the school district at a hypothetical 55 mills

Denver-area totals typically run in the ballpark of 70–120 combined mills depending on the district mix. If your bill changed, check which of the three numbers moved before assuming you know why.

Your value is a two-year photograph of the market — and it expires on odd years.

Colorado does not reappraise property every year. Assessors revalue all real property on a two-year cycle, in odd-numbered years. 2025 was a reassessment year; the next is 2027. In even years your valuation generally carries over unchanged unless the property itself changed — new construction, an addition, a teardown, or a change in land use.

Here is the part that trips people up: a reassessment value is not today's market. Assessors collect sales and market data over an 18-month "base period" from January 1 of the odd year through June 30 of the following even year, then adjust everything to the June 30 appraisal date. The 2025 reassessment reflects the market as of June 30, 2024 — a trailing indicator by design. A sale that closed in October 2024 cannot be considered until the next cycle.

The annual rhythm follows from there. Notices of valuation (NOVs) go out by May 1. Levies get set late in the year, which is why nobody knows the actual bill until winter. Bills are mailed in January, and if the amount exceeds $25 you can pay in full by April 30 or in two installments — the first by the last day of February, the second by June 15.

Gallagher is dead. The legislature holds the dial now.

From 1982 to 2020, the Gallagher Amendment pinned Colorado's residential and non-residential tax shares to a 45/55 ratio. As residential values outran commercial ones, the residential assessment rate kept dropping to hold the balance — from 21% down to 7.15%. In November 2020, voters approved Amendment B, repealing Gallagher and handing the rate dial to the state legislature, with rates frozen at 7.15% residential and 29% non-residential. TABOR still requires a statewide vote for any rate increase.

What followed was a string of temporary relief measures as home values surged. In 2024 the residential rate was 6.7% applied after a $55,000 value subtraction. In 2025 the system split in two — 6.25% for local-government levies and 7.05% for school-district levies — after statewide value growth stayed under 5%.

For 2026 and beyond, under the under-5%-growth branch of the law that is now in effect:

Local-government levies: 6.8% applied to your actual value minus the lesser of 10% of the actual value, $70,000 (adjusted for inflation in later reassessment cycles), or the amount that would reduce the assessed value to $1,000.
School-district levies: 7.05% applied to the full actual value, with no exclusion, locked in for future years.
Commercial property: the assessment rate steps down to 25% in 2026 (most other nonresidential property is at 26% in 2026, then 25% from 2027).

Newer laws also cap how fast local-government property tax revenue can grow — 5.25% per reassessment cycle for non-school local governments, with a separate limit for school districts. The caps restrain district budgets; they do not cap your individual bill.

The split rates are the part everyone misses: the exclusion only shields the local-government portion of your bill. The school-district portion is taxed on the full value.

Think the number is wrong? You get one short window.

If the actual value is off, your recourse is the protest process — and it is calendar-driven:

By May 1: the assessor mails the notice of valuation.
By June 8: file your protest with the county assessor — delivered, postmarked, or in person. The form is included with the notice, but you are not required to use it.
By the last working day in June: the assessor mails a notice of determination.
By July 15: appeal to the county board of equalization if you disagree (some counties use alternate procedures with later deadlines — your notice spells it out).
Within 30 days of the board's decision: further appeal to an arbitrator, district court, or the Board of Assessment Appeals.

What moves an assessor is evidence, and only the right kind counts. Bring comparable sales from the statutory data-collection period — not your Zestimate, not last month's listings, not an appraisal dated after the June 30 cutoff. For the 2025 reassessment, that meant sales between January 1, 2023 and June 30, 2024. Your own purchase price during that window is strong evidence; a purchase after it is not admissible for that cycle. Document condition problems and factual errors — wrong square footage, a finished basement that does not exist.

Remember what you are protesting: the valuation, not the tax amount. Assessors cannot adjust your mill levies or decide your taxes are too high. And if you miss the window, you generally wait for the next one — there is no do-over in September for a valuation protest.

The senior exemption is real — and it is fragile.

Colorado's senior homestead exemption, approved by voters in 2000, exempts 50% of the first $200,000 of actual value from property taxes for qualifying homeowners. To qualify, you must be 65 or older as of January 1 of the tax year and have owned and occupied the home as your primary residence for the last 10 consecutive years. Qualifying disabled veterans, surviving spouses of qualifying veterans, and Gold Star surviving spouses are also covered.

Here is the catch: the exemption lives in the constitution, but its funding is appropriated year to year by the legislature, which reimburses local governments for the forgone revenue. Lawmakers have suspended it during budget crunches before, and county assessors describe it as funded and active for 2026 while warning that state budget pressure could change that. It is a year-to-year question, not a guarantee — confirm with your county assessor before counting on it.

One more thing seniors should know: the exemption has historically not moved with you — selling and downsizing restarts the 10-year clock. A temporary portability program (SB 24-111) covers the 2025 and 2026 tax years, and a constitutional amendment for permanent portability was referred to the November 2026 ballot. If you are thinking about moving, that vote matters.

Applications go through your county assessor — file once, and it stays in effect until your status changes.

Colorado property tax FAQ

When are Colorado property taxes due?

Bills are mailed in January for the prior year. If the amount is more than $25, pay in full by April 30 or in two halves — the first by the last day of February, the second by June 15. Amounts of $25 or less are due in full April 30.

Why did my taxes go up when assessment rates went down?

Because rates are only one variable. The temporary $55,000 value subtraction expired after 2024, and if your actual value rose, that increase can outweigh the lower rate. A split rate system also means the school-district portion of your bill is now assessed at 7.05% on the full value — and schools are typically the largest line on the bill.

Can my assessed value drop if the market falls?

It can, but only at reassessment — the next one is 2027 — and only if the downturn shows up in the data-collection period ending June 30, 2026. A market dip this fall will not appear until the following cycle.

What if I miss the June 8 protest deadline?

You generally lose the right to contest that year's valuation. There is no late-filing grace period for real-property protests. Mark May 1 — when notices of valuation go out — as the starting gun, and file early rather than waiting on the deadline.

Does the senior homestead exemption apply to a second home or rental?

No. It applies only to the primary residence you have owned and occupied for the last 10 consecutive years, and only for one property. Investment properties and second homes do not qualify.

Colorado property taxes, explained without the fog.