Property Tax Spikes in Colorado: How Reassessments & Expirations Impact Payments

It usually starts with an envelope from the county. The Notice of Valuation says your home is suddenly "worth" far more than you remember paying for it. A few months later, your mortgage servicer follows up with the real punchline: your escrow account is short, and your monthly payment is going up to cover it.

If that sequence has played out in your mailbox recently, you're not alone, and you didn't do anything wrong. Colorado property tax bills move in lurches rather than smooth lines, and two separate mechanisms collided to make the bills payable in 2026 feel especially brutal: the state's odd-year reassessment cycle and the expiration of temporary tax relief that had been quietly shielding part of your home's value.

Understanding both is the difference between panicking at a number and actually being able to plan around it. Here's how the machine works.

The 2-year clock: odd-year reassessments and intervening years

Colorado does not revalue your home every year. County assessors operate on a two-year cycle:

• Odd-numbered years are revaluation years. In a year like 2025, the assessor sets a new actual value for every property in the county.
• Even-numbered years are intervening years. In a year like 2026, your value generally stays frozen at the prior year's figure. It only changes if something structural changed — an addition, a new garage, a major remodel the county catches on a permit.

The part that surprises most homeowners is which sales the assessor is allowed to look at. The 2025 revaluation wasn't based on what homes were selling for in 2025. By law, appraisals were anchored to market sales that closed between July 1, 2022 and June 30, 2024. So the value driving your current bill is a snapshot of a market window that may already feel like ancient history — and if your neighborhood ran hot during that window, your valuation captured the peak, whether or not prices have cooled since.

This is why Colorado tax bills feel like a staircase instead of a ramp. Nothing moves for a year, then everything moves at once. If you budget as though this year's bill is a stable baseline, the next odd year will catch you off guard — every time.

The hidden culprit: the $55,000 exemption that quietly expired

Reassessment alone doesn't explain the size of the jump many homeowners saw on bills payable in 2026. The second mechanism is less visible and, frankly, easier to miss: temporary legislative tax relief expired.

For the 2023 and 2024 tax years, state lawmakers softened the blow of rising valuations by exempting a slice of every home's actual value from taxation — relief that, at its peak, shielded up to $55,000 of a property's actual value. The mechanics were invisible to most people: you didn't apply for it, it just quietly lowered the taxable base your bill was computed from.

Then it ended. When that exemption rolled off, the full actual value of your home went back on the table — at the same moment the 2025 revaluation pushed that value higher. Two steps up, taken together. That's why so many of the spikes landing in 2026 felt disproportionate to anything visible in the housing market: part of the increase isn't the market at all. It's a discount disappearing.

One more wrinkle worth knowing: Colorado now applies a split assessment, with distinct treatment for school district taxes versus non-school district taxes. Practically, it means your bill is no longer one simple calculation but two parallel ones — and it's another reason two neighbors with similar homes can open meaningfully different bills.

Calculating the math: assessed value × mill levy

The formula itself is mercifully short:

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

A mill is one dollar of tax per $1,000 of assessed value, and your total mill levy is the stack of every taxing district you live in — county, school district, fire protection district, water district, and so on. Here's a simplified, hypothetical example to show how the expired exemption moves the needle. (The assessment rate and mill levy below are round illustrative numbers, not your county's actual figures — those vary by district and year, so check your own Notice of Valuation.)

In this illustration, nothing about the house or the market changed — yet the bill rises by roughly $308 a year, about $26 a month, purely because the exemption rolled off. Layer a higher 2025 valuation on top and the staircase gets steeper. And because most homeowners pay property taxes through escrow, the increase doesn't arrive as a tax bill you can see coming. It arrives as a mortgage payment increase, often bundled with an escrow shortage from the prior year that gets repaid on top.

Property taxes are also one of the line items that separate cheap-looking towns from genuinely affordable ones. If you're comparing places to live, our breakdown of the true cost of mountain living in Denver versus Colorado's ski towns shows how taxes, insurance, and utilities stack on top of the sticker price of housing.

How and when to appeal your valuation

You cannot appeal the mill levy — that's set by your taxing districts and by voters. What you can challenge is the actual value the assessor assigned to your home. And the appeal isn't a complaint form; it's an evidence exercise.

1. Read your Notice of Valuation carefully. Check the basics first: square footage, bedroom and bathroom count, lot size, condition. Assessors value thousands of properties by model — factual errors happen, and they're the easiest wins.
2. Pull comparable sales from the legal window. This is the step most appeals get wrong. For the 2025 revaluation, the assessor can only consider sales from July 1, 2022 through June 30, 2024. A bargain sale on your street last month is irrelevant; three comps from inside the window are persuasive.
3. Choose genuinely comparable properties. Similar size, age, condition, and neighborhood. If your comps needed a new roof and yours didn't, expect the assessor to adjust accordingly.
4. Submit to the County Assessor by the deadline. The protest window opens in the spring after notices go out and is short — check your county assessor's website for this year's exact dates and accepted formats (many counties take appeals online).
5. Escalate if you disagree with the answer. If the assessor denies your protest, you can take the case onward to the County Board of Equalization. Same evidence, fresh audience.

One honest caveat: a successful appeal lowers your valuation, not your mill levy, and it won't bring back an expired exemption. It's a real lever — just not a magic one.

The bottom line: re-budget before the escrow letter does it for you

A Colorado property tax spike is rarely one thing. It's a two-year reassessment clock, a sales window that captured a hot market, and temporary relief expiring on schedule — all converging on a single escrow statement. You can't vote any one of them away by ignoring the envelope.

What you can do is treat your housing line item as a moving target. If your escrow payment jumped — or you suspect it's about to — rerun your monthly numbers now rather than after the shortage letter lands. And while you're at it, check the other half of your escrow: if rebuild costs have climbed alongside valuations, our guide to whether your Colorado home is underinsured against today's replacement and rebuild costs covers the gap that hurts far more than any tax bill.