Opposing Colorado tax laws to face off on Nov. 3 ballot

Colorado voters will decide between two mutually exclusive visions for the state's tax code on November 3, after both competing ballot measures cleared signature thresholds this week. Amendment 39 would impose a new 5.55 percent flat tax on investment income—capital gains, dividends, and interest—generating an estimated $140 million annually for public education. Amendment 40, backed by business groups and the state chamber of commerce, would cap income tax rates at their current 4.4 percent level and prevent future increases without voter approval. Only one can pass; if both clear 50 percent support, the one with more votes wins.

The signatures themselves tell a story about where Colorado's political energy sits. Amendment 39 gathered its required 124,632 valid signatures primarily from Denver and Boulder metro areas, where progressive organizing infrastructure dominates. Amendment 40 drew support from suburban and exurban counties, counties that have become swing territory in recent election cycles. The fact that both measures cleared signature requirements—no small feat in a state of 3.7 million people—suggests genuine voter division on whether Colorado's tax burden should shift toward investment income or remain locked in place.

This battle has roots in 2022's failed Proposition KK, a similar investment income tax that voters rejected 55-45 after business groups and conservative economists ran heavy advertising warning of capital flight and portfolio impacts. The education lobby learned from that loss and restructured Amendment 39's pitch around K-12 funding rather than broad revenue. But the underlying dispute remains: whether Colorado can tax its way to better schools without economic consequence, or whether growth and opportunity depend on tax restraint.

The conservative argument here is straightforward: Colorado has no revenue problem, it has a spending problem. State revenues have climbed 30 percent over the past decade, outpacing population growth. Teachers' salaries have risen; the real issue is how dollars flow through a bloated bureaucracy. Amendment 40 simply prevents politicians from raiding investment accounts during the next crisis—and there will be one. The business community isn't opposed to education funding; it's opposed to being singled out as the funding mechanism while income tax rates remain "temporary" and perpetually renewable. That's the pitch working in suburbs and mountain towns.

Watch for how early voting breaks on these measures. Colorado conducts all-mail elections, so ballots arrive in late September. The first two weeks of October will show whether Amendment 39 can replicate the voter enthusiasm that carried Proposition 314 (the school funding measure) to victory in 2020, or whether Amendment 40's anti-tax message gains traction as inflation and recession fears mount. The education lobby needs 50 percent plus one in a mail election where turnout may be lower than presidential years. A late October Denver Post or KCNC-TV poll showing either measure below 48 percent will signal the other may prevail.

The real stakes: Colorado's fiscal direction for the next decade. If Amendment 40 passes, future legislatures lose a lever they've relied on, and schools dependent on new revenue sources must make do with existing appropriations or pursue property tax increases—which face their own voter skepticism. If Amendment 39 passes, Colorado joins Minnesota and Washington as states with dedicated investment income taxes, and the business community begins contingency planning around tax competitiveness with neighboring states. Neither outcome is inevitable.