Proposition MM: What It Means for Douglas County Taxpayers

Colorado voters approved Proposition MM on November 4, 2025, by roughly 60 percent to 40 percent (about 59.7% yes to 40.3% no). For most Douglas County households the measure changes nothing. But for higher-income residents, it meaningfully raises what they owe the state starting with the 2026 tax year.

What Proposition MM changed

Proposition MM reduces the Colorado itemized or standard income tax deduction to just $1,000 for single filers and $2,000 for joint filers for taxpayers with federal taxable income of $300,000 or more. It does not change Colorado's flat 4.4% tax rate; instead, it raises taxable income for high earners by limiting what they can deduct.

This is the second cut in a few years. The progression for filers over the $300,000 threshold looks like this:

• Before Proposition FF (2022): deductions capped at $30,000 (single) / $60,000 (joint)
• After Proposition FF: capped at $12,000 (single) / $16,000 (joint)
• After Proposition MM (2026): capped at $1,000 (single) / $2,000 (joint)

Who it affects and by how much

The change applies only to taxpayers with federal taxable income of $300,000 or more. According to nonpartisan legislative staff estimates, the average affected single filer would owe about $327 more and the average joint filer about $574 more per year.

The measure is expected to raise roughly $95 million a year, dedicated to the state's Healthy School Meals for All program (free breakfast and lunch for public-school students) with any excess going to SNAP food assistance. A companion measure on the same ballot, Proposition LL, also passed and lets the state keep revenue already collected for the school-meals program.

What it means locally

Douglas County has one of the higher concentrations of high-income households in Colorado, so a larger share of local filers clear the $300,000 line than in most parts of the state. For those households, the practical effect is a modestly higher Colorado tax bill beginning with 2026 returns, and less value from itemizing at the state level.

For a breakdown of how Proposition MM interacts with the rest of the 2026 changes — including the Social Security and pension subtractions that newly benefit retirees — a Douglas County wealth-management firm has published a 2026 Colorado tax-changes guide aimed at high earners and retirees.

This article is general information, not tax advice. Confirm how the change applies to your situation with a qualified tax professional or the Colorado Department of Revenue.