The short version: file when your value benchmarks well above same-type, same-size peers and the two-year savings clearly outrun the effort. Skip when you benchmark fairly, when the cycle dollars are small, or when the income-and-expense disclosure the county board compels would cost more than the reduction returns. The feared outcome, the county raising your value because you appealed, shows up in 8 of 8,058 state-board filings for tax year 2023, and Colorado caps any increase on escalation at 5% above the county board's figure. The rest of this page is that rule with real numbers.
Step 1: Benchmark before you argue
An appeal is a claim that your value is wrong. The fastest evidence either way is where you sit against comparable properties. The free assessment check ranks any of 19,939 Colorado commercial properties against same-type, same-size cohorts from certified county rolls: statewide, large industrial buildings (150,000+ SF) carry a median value around $105 per square foot, large offices about $137, and every county and size band has its own number. Ranking at the 60th percentile is not a case. Ranking at the 90th, with no story that explains it, usually is.
Step 2: Run the two-year math
Colorado values on a two-year cycle, so a reduction won in the reassessment year holds for both years. The arithmetic on a mid-size building: a property assessed at $10 million actual value carries $2.5 million assessed (the 25% commercial-classed ratio for 2026; industrial-classed buildings assess at 26%), which at a 90-mill levy is about $225,000 a year of tax. A 10% value reduction returns roughly $45,000 over the cycle; on the published 18% tier for that liability you keep about $36,900 of it, and an unsuccessful appeal costs nothing. At the small end the math still clears: a $95,000 tax bill over-assessed by 10% returns about $9,500 a year, of which you keep about $7,600 annually.
Step 3: Weigh the two real risks
Disclosure. The assessor-level protest is free and reveals little. Escalate to the county board, and Colorado compels income and expense disclosure. For some owners that is nothing; for others it is the whole decision. Know which you are before filing, not after.
The raise. Owners fear appealing will increase their value. The statewide record says that fear is overpriced: of 8,058 commercial Board of Assessment Appeals (BAA) cases for tax year 2023, 8 ended in a raise, about one in a thousand, and it is screenable in advance. The market as a whole settled 61% of those appeals.
Step 4: Know the honest no
Skip the appeal when the benchmark says you're fairly assessed (a memo saying so is worth keeping for lenders and auditors); when the cycle savings wouldn't cover the attention it costs your team; or when disclosure sensitivity outweighs the dollars. A contingency firm that files everything is running a lottery with your county relationships. In Colorado, roughly one in three properties we review gets no recommendation to file, and that share is structural, not timidity, because it varies enormously by state: in a capped state like Arizona, where the taxable limited value usually sits well below the appealable full cash value, the honest answer is “don’t file” as often as nine times in ten; a paper reduction that never reaches the bill is not a win. A review that ends in “don’t file” is not wasted; it is the reason the recommendations to file get taken seriously.
The 2027 clock
Colorado's next reassessment notices mail May 1, 2027, with protests due June 1, 2027, and the evidence that will decide those values (the June 30, 2026 data date) already exists. Files built before the notices land argue from preparation; files opened after argue against a deadline. The free assessment review now is how you know which side of that you'll be on.