DOR Taxation web site

Filing

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Colorado's individual income tax return starts with your federal taxable income. Therefore, your federal deductions and personal exemptions have already been subtracted. For this reason, no lines for deductions and personal exemptions appear on the Colorado form. It is important to complete your federal income tax return first so that you will know your federal taxable income.
Then, on Colorado's 104 form or Colorado individual income tax electronic filing options, the state requires certain additions to federal taxable income and offers subtractions from federal taxable income before you arrive at your Colorado taxable income. Your Colorado taxable income is then taxed at a flat rate of 4.63%.

 

Depending on how much income tax you told your employer(s) to withhold during the year or depending on how much estimated income tax you paid if you are self-employed, you will either receive a refund or owe tax.

 

Colorado income tax should be filed by April 15. If that date falls on a weekend or holiday, the tax should be filed by the next business day.

 

To avoid processing delays, please see Common Filing Errors.

 

Information regarding the Department of Revenue's transition to a new tax accounting system.