Colorado's Income Tax Structure

Colorado has a flat income tax rate of 4.40% on all taxable income, regardless of how much you earn. This rate applies to wages, self-employment income, investment gains, and other sources of taxable income. Unlike some states that use a tiered system where higher earners pay higher percentages, Colorado taxes everyone at the same rate.

The 4.40% rate has been in place since 2023, when Colorado voters approved a temporary reduction through the TABOR (Taxpayer Bill of Rights) refund mechanism. Before that, the rate was 4.63%. The rate can change year to year depending on state revenue and voter-approved adjustments, so it's worth checking the Colorado Department of Revenue website if you're planning ahead.

Key Takeaways

  • Colorado's flat tax rate of 4.40% applies to all income levels, meaning a person earning $30,000 and a person earning $300,000 pay the same percentage.
  • The rate applies to wages, self-employment income, rental income, capital gains, and most other forms of taxable income reported on your federal return.
  • Colorado does not tax Social Security benefits, military pensions, or certain retirement income, which can lower your overall state tax burden.
  • Your actual Colorado tax bill depends on your federal taxable income, deductions, and credits you claim on your state return.
  • The rate can change annually based on state revenue surpluses and voter-approved tax measures, so verify the current rate when filing.

What Income Gets Taxed in Colorado

Colorado taxes most forms of income at the 4.40% rate, including W-2 wages from your employer, self-employment income, interest and dividends, rental income, and capital gains from selling stocks or property. The state starts with your federal taxable income and then applies Colorado-specific deductions and credits.

Some income sources are exempt from Colorado tax. Social Security benefits are not taxed, regardless of your income level. Military pensions and certain federal employee pensions also receive special treatment. If you receive income from a pension or retirement account, check the Colorado Department of Revenue's guidelines, because some retirement income qualifies for partial or full exemption depending on your age and the source of the pension.

How to Calculate Your Colorado Tax

Your Colorado income tax is calculated by taking your federal taxable income, explore Colorado-specific adjustments and deductions, and multiplying the result by 4.40%. You don't calculate it from scratch—you use your federal return as the starting point and then make state-specific changes on your Colorado return.

The easiest way to understand your liability is to look at your federal Form 1040 and the schedules you filed with it. Colorado generally follows federal rules for what counts as income and what you can deduct. However, Colorado allows some deductions that the federal government doesn't, and vice versa. For example, Colorado offers a dependent exemption credit that reduces your tax, while the federal government uses a standard deduction instead. When you file your Colorado return (Form 104), you'll work through these adjustments line by line.

Standard Deduction and Credits in Colorado

Colorado offers a standard deduction that reduces your taxable income before the 4.40% rate is applied. For the 2023 tax year, the standard deduction is $3,850 for single filers and $7,700 for married couples filing jointly. These amounts adjust slightly each year for inflation. If your total income is below the standard deduction, you may owe no Colorado income tax at all.

Beyond the standard deduction, Colorado offers several credits that directly reduce your tax bill. The dependent exemption credit gives you a credit for each dependent claimed on your federal return. The earned income tax credit (EITC) is available to lower-income workers and is calculated based on your federal EITC. Colorado also offers credits for property tax paid, child care expenses, and other specific situations. Credits are more valuable than deductions because they reduce your tax dollar-for-dollar rather than just reducing your taxable income.

Self-Employment and Business Income

If you're self-employed or own a business in Colorado, you pay the 4.40% state income tax on your net business income (revenue minus deductible business expenses). You also owe federal self-employment tax, which is separate. Colorado does not charge a separate self-employment tax on top of the income tax.

Self-employed filers should report their income on Schedule C (federal) and then carry that net income to their Colorado return. You can deduct legitimate business expenses—supplies, equipment, home office, vehicle mileage, and other ordinary costs—before calculating your Colorado tax. Keep records of all expenses because Colorado follows federal rules for what qualifies as a deductible business expense.

When the Tax Rate Changes

Colorado's income tax rate is not fixed permanently. The state constitution includes TABOR, which limits how much revenue the state can keep. When revenue exceeds the limit, the state must refund the surplus to taxpayers. This mechanism has caused the tax rate to fluctuate in recent years.

In 2023, the rate dropped from 4.63% to 4.40% due to a TABOR refund. The rate could change again in future years depending on state revenue performance and whether voters approve any tax measures. Before filing, check the Colorado Department of Revenue website to confirm the current year's rate, because using an outdated rate will result in underpayment or overpayment of your taxes.

Filing Your Colorado Return

Colorado residents file Form 104 (Colorado Individual Income Tax Return) along with their federal return. You'll need your federal return information, W-2s or 1099s, and documentation of any Colorado-specific deductions or credits you claim. The filing important date is the same as the federal important date—typically April 15.

You can file by mail, through the Colorado Department of Revenue's online system, or through tax software that supports Colorado returns. If you owe money, you can pay online, by mail, or through an installment plan. If you're due a refund, filing electronically typically results in faster processing than mailing a paper return.

Frequently Asked Questions

Does Colorado tax retirement income and pensions?

Colorado does not tax Social Security benefits. Military pensions and certain federal employee pensions are also exempt. Other pension and retirement account income may be partially exempt depending on your age and the source. Check the Colorado Department of Revenue's pension exemption rules for your specific situation.

What's the difference between Colorado's tax rate and the federal rate?

Colorado's 4.40% is a state tax separate from federal income tax. You owe both. Your federal rate depends on your income bracket and filing status and ranges from 10% to 37%. The two taxes are calculated independently on different forms.

If I live in Colorado but work in another state, which state taxes my income?

Generally, the state where you work taxes your income. If you're a Colorado resident working in another state, you may owe tax to that state. Colorado offers a credit for taxes paid to other states to avoid double taxation. File a return in both states and claim the credit on your Colorado return.

Do I have to file a Colorado return if I don't owe any tax?

You're not required to file if your income is below the standard deduction. However, if you had taxes withheld from your paychecks, filing a return will get you a refund. If you're due any credits, filing is also worthwhile even if you owe no tax.

Can I deduct property taxes or mortgage interest on my Colorado return?

Colorado does not allow a deduction for property taxes or mortgage interest on your state return. However, Colorado offers a property tax credit if you meet income limits. The credit is based on the property taxes you paid, not a deduction. Check whether you may have access to on the Colorado Department of Revenue website.