How to Find Comparable Sales for a Colorado Property Tax Appeal

Comparable sales are the backbone of almost every successful Colorado appeal. But not all comps count — the wrong ones get your case denied with a form letter. Here's how to find the ones that win.

Use the right time window

This is the rule most people get wrong. Colorado values residential property using sales from an 18-month data-gathering period ending June 30 of the year before reassessment — not today's sales. A great comp from last month is irrelevant if it's outside the statutory window. Pull sales from the correct period; assessors may reach back further only when comps were scarce.

What makes a comp truly comparable

• Proximity — same neighborhood or subdivision beats same ZIP; same street is best.
• Size — within roughly 10–15% of your finished square footage.
• Age & style — similar year built and construction type (ranch vs. two-story, etc.).
• Beds/baths and key features — garage, basement finish, lot size in the same ballpark.
• Arm's-length sale — exclude foreclosures, family transfers, and other non-market sales.

Where to find them

• Your county assessor's sales search and the recorded sales on comparable parcels (start from our county guides).
• Public real-estate listing sites for sold prices and dates — verify the close date falls in the window.
• A local agent's MLS pull, if you have one, filtered to the statutory period.

Adjust honestly

If a comp is bigger, newer, or has a finished basement and yours doesn't, acknowledge it and adjust downward — a credible, slightly conservative case beats an aggressive one the board can poke holes in. Pair strong comps with any documented condition issues for the strongest argument.

Let us build the comp set

Finding window-correct, truly comparable sales is the most time-consuming part of a DIY appeal. Enter your address and we assemble the comps, make the adjustments, and present them the way boards expect — no upfront fee.