The tax rate would increase to 7.4% for households earning over $500,000, and up to 8.4% for those earning $1 million or more. Under those changes, a household making $1 million annually would pay $15,925 more in income taxes, according to the coalition’s calculator. Supporters of a graduated income tax proposal rally outside the Colorado Capitol on March 17, 2026. Advance Colorado delivered nearly 190,000 signatures, which are under review, to place its counter measure capping the state’s income tax rate on the November ballot. If approved this year, the graduated income tax measure would be one of the most seismic changes to Colorado’s tax policy since TABOR’s enactment more than 30 years ago.