Colorado Income Tax Calculator 2026

Colorado taxes your federal taxable income

Colorado's income tax return (Form DR 0104) begins with federal taxable income, the bottom line after your federal standard or itemized deductions. Colorado then adds back a few items, subtracts a few others, and applies a single 4.40% rate. In practice this means the federal $16,100 standard deduction ($32,200 for joint filers) works as Colorado's standard deduction too.

Example: a married couple with two children and $110,000 of wages has federal taxable income of $77,800 after the joint standard deduction. Colorado tax is $77,800 × 4.40% = $3,423, or 3.11% of wages, before any Colorado credits such as the state child tax credit or earned income credit.

Colorado retirement and Social Security subtractions

Colorado gives retirees one of the larger state subtractions. The caps below come from the legislature's nonpartisan staff (February 2026); the Social Security income limits apply from tax year 2025, per the Department of Revenue:

• The subtraction covers PERA benefits, private pensions, IRA and 401(k) distributions and annuities. Survivor benefits qualify at any age.
• Social Security you subtract reduces the room left for other pension income under the same cap, so you choose whichever produces the larger subtraction.
• In tax year 2023, 573,941 Colorado taxpayers claimed an average pension subtraction of $24,934, saving about $1,097 each.

TABOR and why Colorado's rate can change

Colorado's Taxpayer's Bill of Rights (TABOR) caps how much revenue the state may keep. When revenue exceeds the cap, the excess must be refunded, and state law uses several mechanisms to do it, including temporary income tax rate reductions and refunds on the income tax return. That is why the Colorado rate has been cut temporarily in some years and why your return may include a TABOR refund line. The calculator uses the standard rate and does not include any TABOR refund.

Part of Colorado income tax is outside TABOR: one-third of 1% of Colorado taxable income goes to the State Education Fund and one-tenth of 1% to affordable housing programs.

Filing, extensions and part-year residents

Colorado returns for 2026 are due April 15, 2027. You get an automatic six-month extension to October 15 with no form to file, but only if at least 90% of your tax is paid by April 15; otherwise penalties apply.

Part-year residents and nonresidents file the regular DR 0104 together with Form DR 0104PN, which prorates the tax based on the share of income that is Colorado-source or received while living in Colorado.

High earners should know that Colorado requires some taxpayers to add back part of their federal itemized or standard deduction, and it does not follow every federal deduction, such as the qualified business income deduction. Those adjustments are not in the calculator.