Colorado has a state income tax, and it applies to most residents and income earned in the state

Colorado taxes income at a flat rate of 4.63% as of 2024. This rate applies to wages, self-employment income, investment gains, and most other forms of income. The rate is the same whether you earn $30,000 or $300,000 — Colorado does not use tax brackets the way many other states do.

If you live in Colorado and earn money there, you owe state income tax on that income. If you live outside Colorado but earned money inside the state, you may owe Colorado tax on that specific income. The Colorado Department of Revenue administers the tax and processes returns through Form 104, the state's basic income tax return.

The flat-rate structure means your state tax bill is straightforward to calculate: take your taxable income and multiply by 4.63%. However, what counts as "taxable income" depends on federal rules, deductions you claim, and credits you may receive.

Key Takeaways

  • Colorado's state income tax rate is a flat 4.63% on all taxable income, with no tax brackets based on income level.
  • You owe Colorado income tax if you are a resident or if you earned income within the state during the tax year.
  • Colorado taxable income starts with your federal taxable income and then applies state-specific adjustments and deductions.
  • Colorado offers a standard deduction and various credits that can reduce your taxable income below what you report to the IRS.
  • You file Colorado taxes on Form 104 (or Form 104-ES for estimated tax) by April 15 unless you receive an extension.

Who must file a Colorado state income tax return

You must file a Colorado return if you are a resident and your income exceeds the standard deduction for your filing status. Residency in Colorado means you lived in the state for more than six months of the tax year, or you maintained a permanent home there and spent significant time in the state.

Non-residents must file if they earned income in Colorado during the year, even if they lived elsewhere. This includes people who worked in Colorado for part of the year, received rental income from Colorado property, or had business income from Colorado sources. The amount of income does not matter — if you earned any Colorado-source income and it exceeds a small threshold, you file.

The standard deduction for Colorado in 2024 is $3,850 for single filers and $7,700 for married filing jointly. These amounts change each year. If your total income is below the standard deduction for your filing status, you do not have to file a state return, though filing may still benefit you if you are due a refund.

Colorado's standard deduction and tax credits

Colorado allows you to claim a standard deduction that reduces your taxable income before the 4.63% rate is applied. Unlike the federal standard deduction, which varies by age and filing status, Colorado's standard deduction is the same for all taxpayers in each filing status category. You can also itemize deductions if they exceed the standard deduction, though most Colorado taxpayers use the standard deduction.

The state offers several credits that directly reduce your tax bill. The Colorado earned income tax credit (EITC) mirrors the federal credit and provides money back to lower-income working people. The child dependent credit gives $24 per dependent child. The property tax exemption for seniors and disabled persons can reduce or eliminate state income tax for those who meet income and age requirements. Credits are applied after you calculate your tax, so they lower your final bill dollar-for-dollar.

Some income is exempt from Colorado tax entirely. Social Security benefits are not taxed by Colorado. Military retirement pay is not taxed. Certain pension income may be exempt if you meet age and income requirements. When you file, you report these amounts separately so they do not count toward your taxable income.

How Colorado income tax interacts with federal tax

Colorado starts with your federal taxable income as reported on your federal return, then makes adjustments. Some deductions allowed by the IRS are not allowed by Colorado, and vice versa. For example, if you paid state income tax to another state, you can deduct that on your federal return, but Colorado does not allow you to deduct Colorado income tax paid to Colorado.

The most common adjustment is the federal tax deduction. If you itemize deductions on your federal return and claimed state and local taxes (SALT), Colorado requires you to add back the Colorado income tax portion of that deduction. This prevents you from deducting Colorado tax from Colorado income, which would create a circular benefit.

If you moved to Colorado from another state during the year, you may owe tax to both states on the income earned in each state. Some states offer credits for taxes paid to other states to prevent double taxation, but you must file in both states and claim the credit on the state that taxes your worldwide income.

Filing important date and estimated tax payments

Colorado income tax returns are due by April 15 of the year following the tax year, the same important date as federal returns. If you file a federal extension (Form 4868), your Colorado return is automatically extended to October 15. You must request the extension by April 15, even if you cannot pay the full amount owed.

If you expect to owe $500 or more in Colorado income tax for the year and you do not have enough tax withheld from paychecks or other income, you must make estimated tax payments. These are quarterly payments due on April 15, June 15, September 15, and January 15. You file Form 104-ES to calculate and report estimated payments. Failure to pay estimated tax when required can result in penalties and interest.

If you are self-employed or have income not subject to withholding, you are responsible for calculating and paying estimated tax. Employees can adjust their withholding through their employer's W-4 form to avoid a large bill at tax time. The Colorado Department of Revenue website has a withholding calculator to help you determine the right amount.

Special situations: part-year residents and non-residents

If you moved to Colorado during the year, you are a part-year resident. You report income earned before you moved as non-resident income and income earned after you moved as resident income. Both are taxed by Colorado, but the calculation method differs. Non-resident income is taxed only on the Colorado-source portion, while resident income is taxed on worldwide income for the months you were a resident.

Non-residents who worked in Colorado for a short time or earned rental income from Colorado property must still file Form 104. You report only the income earned in Colorado, not income from other states. If your employer withheld Colorado tax from your paychecks, you file to report that withholding and claim a refund if you overpaid.

Military members stationed in Colorado are treated as residents for tax purposes if they meet residency requirements, even if they maintain a home in another state. Spouses of military members may have different rules depending on whether they are also stationed in Colorado or living there independently.

What happens if you do not file or pay

If you owe Colorado income tax and do not file or pay by the important date, the Colorado Department of Revenue assesses penalties and interest. The failure-to-file penalty is typically 5% of the unpaid tax per month, up to 25%. The failure-to-pay penalty is 0.5% per month. Interest accrues daily at a rate set by the state, currently around 8% annually, though this rate changes quarterly.

If you file late but pay the full amount owed, the penalty is reduced. If you have a valid reason for missing the important date — illness, natural disaster, or military service — you may request penalty relief from the Department of Revenue. You must submit a written request with documentation of the reason.

The state can place a lien on your property, garnish your wages, or intercept your federal tax refund to collect unpaid Colorado income tax. If you owe back taxes, contacting the Department of Revenue to set up a payment plan is usually faster and less costly than waiting for enforcement action.

Frequently Asked Questions

Does Colorado tax retirement income differently than wages?

Colorado taxes most retirement income at the same 4.63% rate as wages. However, Social Security is not taxed, and military retirement pay is exempt. Some pension income may be exempt if you are over 55 and meet income limits. You report these amounts on your return to show they are not subject to tax.

What if I worked in Colorado but lived in another state?

You owe Colorado income tax on the money you earned in Colorado. File Form 104 as a non-resident and report only Colorado-source income. If your employer withheld Colorado tax, that withholding is credited against your Colorado tax bill. You may also owe tax to your home state on the same income, depending on that state's rules.

Can I deduct federal income tax paid from my Colorado taxable income?

No. Colorado does not allow a deduction for federal income tax. However, if you itemize deductions on your federal return, you may have claimed state and local taxes (SALT). Colorado requires you to add back the Colorado income tax portion of that deduction when calculating Colorado taxable income.

Do I have to pay estimated tax if I am self-employed?

Yes, if you expect to owe $500 or more in Colorado income tax and do not have enough withheld from other sources. You make quarterly payments on Form 104-ES by April 15, June 15, September 15, and January 15. The form includes a worksheet to calculate the correct payment amount based on your expected income.

What if I moved out of Colorado during the year?

You are a part-year resident and file Form 104. Report income earned while you lived in Colorado as resident income and income earned after you moved as non-resident income. Both are taxed by Colorado, but only the Colorado-source portion of non-resident income is taxed. Include documentation of your move date with your return.