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# Colorado Property Tax Reassessment 2027: The Key Dates
- URL: https://truenorthboulder.com/guides/colorado-property-tax-reappraisal-2027/
- Published: 2026-09-04T09:00:00.000Z
- Updated: 2026-09-04T20:08:16.000Z
- Description: Colorado reappraises every property in odd-numbered years, and 2027 is one. The value is built from sales through June 30, 2026, before a fall-2026 buyer closed. Your notice arrives by May 1, and the protest deadline is June 1, moved up a week from the June 8 most sources still print.
- Author: Daniel Hsieh
- Tags: Answer Brief, Buying, Colorado Law

Around the end of April 2027, an envelope arrives from the county assessor carrying a new value for your home and a deadline for arguing with it. Colorado reappraises all real property in odd-numbered years, and 2027 is one of them. Here is what that number is built from, and which dates on it the statute will not move.

> **The short answer:** Your Notice of Valuation arrives **by May 1, 2027**, and the value on it is built from sales in a window that **ended June 30, 2026**, before you closed, if you bought that fall. Values are adjusted to that date, so the price you just paid is not the evidence most owners assume it is. The deadline to protest is **June 1, 2027** — moved up a week by SB26-046, so most sources still show June 8 — and in Boulder and Larimer the assessor's determination follows by **August 15**, with an appeal to the county board by **September 15** — the date these counties administer, which is worth confirming against your own notice.

## What the 2027 property tax reassessment is made of

Colorado law requires every county to revalue all real property in odd-numbered years, so 2027 is a full reappraisal, not a spot check, and the value it produces rides for two years.

The part worth understanding is the window. Statute sets the "level of value" from the eighteen-month period immediately before July 1 preceding the assessment date, which for 2027 means a window **ending June 30, 2026**. If there aren't enough comparable sales, the assessor may reach further back in six-month increments: [Boulder County](https://bouldercounty.gov/property-and-land/assessor/assessment/?ref=truenorthboulder.com) used a twenty-four-month base period last cycle. So the *start* of the window can stretch. The *end* does not move. And the level of value is adjusted to that final day, which is the detail that decides everything below.

## Why the price you just paid isn't the trump card

If you closed in October 2026, your purchase happened **after** the window that sets your 2027 value had already closed. The assessor is not ignoring your sale; it sits outside the period the statute tells them to use.

That matters because "but I just paid less than this" is the first argument most owners reach for, and on a 2027 notice it is the weakest one an autumn-2026 buyer has. Assessments here are built by comparing sales *inside* the window and adjusting to its final day, not by what any one owner paid.

## The dates to write down

| Milestone                             | Your 2027 date            | Fixed by statute?                                           |
| ------------------------------------- | ------------------------- | ----------------------------------------------------------- |
| Sales window closes                   | June 30, 2026             | **Yes**                                                     |
| Assessment date (who gets the notice) | January 1, 2027           | **Yes**                                                     |
| Notice of Valuation mailed            | by May 1, 2027            | **Yes**                                                     |
| **Protest to the assessor**           | **June 1, 2027**          | **Yes. The right is lost after it**                         |
| Assessor's determination              | **by August 15, 2027**    | **Yes — Boulder & Larimer**                                 |
| Appeal to the Board of Equalization   | **by September 15, 2027** | The date these counties administer — confirm on your notice |
| Treasurer bills your 2027 taxes       | January 2028              | **Yes**                                                     |

One thing that table does not settle: your value is only half of a tax bill. The other half is the levy, set separately by the districts your address sits in, which is why [a mill cap is not the ceiling most buyers think it is](https://truenorthboulder.com/guides/what-a-metro-district-mill-cap-really-means/).

Those last two dates usually depend on a choice each county makes in the spring. But Colorado [requires the later calendar](https://leg.colorado.gov/bill%5Ffiles/113774/download?ref=truenorthboulder.com) in counties over 300,000 during a general reassessment year, measured by the state demographer's most recent estimates, and [Boulder County](https://bouldercounty.gov/property-and-land/assessor/appeals/?ref=truenorthboulder.com) (328,560) and Larimer County (377,292) both clear that line comfortably, so for 2027 neither gets to choose. In an even year the requirement lifts and they revert, which is why Larimer's determination date was August 15 in 2025 and June 30 in 2026\. The August 15 determination date follows from that requirement. The September 15 board-appeal date is the one these counties administer on the later calendar rather than one the statute pins to it directly, so treat it as the working date and confirm it against your own notice.

⚠️ Two dates to keep straight. **June 8 was the deadline through 2026**, and it is still printed on county pages and in older guides that are describing the last cycle rather than this one — including, at the time of writing, Boulder County's own appeals page. For 2027 the date is **June 1**, under [Senate Bill 26-046](https://leg.colorado.gov/bill%5Ffiles/113774/download?ref=truenorthboulder.com), signed March 26, 2026\. Separately, the **business personal property** deadline is later than your home's and is not the same date; if you own business personal property in one of these counties, ask the assessor which calendar applies to it — personal property runs on its own calendar.

## What to do with the notice

- **Check the characteristics before the value.** [Square footage](https://truenorthboulder.com/guides/why-square-footage-doesnt-match-the-county/), finished space, bed and bath count — and you can pull that record today, not in May. A factual error is a cleaner conversation than a valuation argument.
- **Compare against sales that closed inside the window**, not against your own purchase.
- **Put all these dates in your calendar now**, starting with June 1, 2027.
- Past the county board, the next step (the state Board of Assessment Appeals, arbitration, or district court) no longer runs on a flat 30-day clock. SB26-046 replaced it with a later-of formula whose longest branch, December 1, applies to counties on the later calendar. Whether that branch reaches Boulder and Larimer turns on the same cross-reference as the September date above, so **do not calendar December 1 on our say-so**. Ask the board, in writing, what your deadline is when they send your decision. Until they answer, work to 30 days from the date on that decision: under a later-of formula the deadline can never fall earlier than that, so a filing that meets it is timely on any reading. And if 30 days has already passed, do not assume you are out — the formula may still leave you until September 1 or later. Ask the board before you conclude anything.
- **If June 1 has already passed, you are not out of options.** Losing the protest right is not the same as losing every remedy: Colorado requires the notice itself to tell you about the **abatement and refund** process, which is a separate route for an overvalued or erroneous assessment. Ask the assessor about an abatement petition — it runs on its own, longer deadline.

Whether a protest is worth filing is a question for your county assessor and your own tax professional. So are two we won't guess at: any fee to file, and how the process treats your value once you do. Ask before June 1\. What is knowable today is that the window closed in June 2026, and your 2027 dates are already set. If you're weighing the tax side of a move rather than a notice already in hand, [what a bigger home really costs](https://truenorthboulder.com/guides/is-a-bigger-boulder-home-worth-it/) covers the carrying-cost reset.

*True North Boulder is a real-estate team with eXp Realty. This is general information for Boulder and northern Front Range owners, not legal or tax advice; confirm dates and your own situation with your county assessor and a tax professional.*

Common questions

## Frequently asked

When will I get my 2027 Colorado Notice of Valuation?+ 

By May 1, 2027\. Colorado statute requires the county assessor to mail a notice of valuation for real property to every owner no later than May 1 each year, and 2027 is a reappraisal year, so every property in the county is revalued rather than a subset. The notice goes to whoever owns the property on the assessment date, which is noon on January 1, so if you closed in late 2026 the 2027 notice is yours, not the seller's. It states the new value and the date by which you have to object.

What is the deadline to protest a property valuation in Colorado?+ 

June 1 for real property, and it changed recently. Senate Bill 26-046 struck June 8 and inserted June 1, effective January 1, 2027, so 2027 is the first cycle on the earlier date. Your objection has to be delivered, postmarked, or given to the assessor in person no later than June 1, and Colorado statute is explicit that after that date the right to object is lost. Two things to watch. County pages and older guides still show June 8 — correctly, because that was the deadline through 2026 — so check the date printed on your own notice, which statute requires the assessor to state in bold-faced type. And the business personal property deadline is a different, later one on its own calendar; ask the assessor which applies, and do not read your house's date off it.

What sales are used to set my 2027 Colorado property value?+ 

Sales from a window that ends June 30, 2026\. Statute sets the level of value using the eighteen-month period immediately before July 1 preceding the assessment date, and if there aren't enough comparable sales the assessor may reach further back in six-month increments. Boulder County used a twenty-four-month base period in the last cycle. The start of the window can stretch, but the end date does not move, and every sale used is time-adjusted to that closing date.

Can I use my own purchase price to protest my Colorado assessment?+ 

Not the way most owners expect, especially if you bought after June 30, 2026, because that sale falls outside the window used for the 2027 value. Assessors value by comparing sales inside the data-gathering period and adjusting them to its final day, so a later purchase price is not a direct comparison. What is worth checking first is the property's own record: square footage, bedroom and bath counts, finished space, and lot size. A factual error there is a correction request, which is a different and often simpler conversation than a valuation argument.