How to Complete Colorado Tax Forms: DR 0104, DR 0100, and Filing

To complete a Colorado tax form, download the current version from the Colorado Department of Revenue at tax.colorado.gov, work from your finished federal return, apply Colorado’s additions and subtractions to arrive at state taxable income, and file either electronically through Revenue Online or by mail. The form most people need is the DR 0104, Colorado’s individual income tax return, which applies the state’s flat 4.4% rate to your federal taxable income after Colorado-specific adjustments. Businesses collecting sales tax use the DR 0100, and motor vehicle paperwork lives on a separate DMV site.

Where to Get the Right Form

CDOR lists every current tax form in numerical order on its forms page, with a search box that filters by form number or title.¹ A “Forms by Tax Type” page groups them by income, sales and use, withholding, or severance. Only the most recent version appears on the main listing; prior-year forms sit on a separate archive page, which matters if you’re filing a late return or amending an older year.

Most forms are interactive PDFs you can type into before printing or saving. A few older ones are print-only. Colorado updates forms annually for legislative changes, so download a fresh copy each year rather than reusing last year’s file. The revision date prints in small type at the bottom of each form.

Motor vehicle forms live at dmv.colorado.gov under their own numbering system.² Some title documents are classified as “secure” forms and must be purchased through approved vendors like the Colorado Auto Dealers Association rather than downloaded for free.

Completing the DR 0104 Individual Income Tax Return

You file the DR 0104 if you’re required to file a federal return and you were a full-year Colorado resident, a part-year resident who earned income while living here, or a nonresident with Colorado-source income.³ The return leans on your federal 1040: Line 1 of the DR 0104 is your federal taxable income copied from federal Form 1040, Line 15.⁴ Finish the federal return first.

What to Gather Before You Start

Your completed federal return, since the DR 0104 pulls line numbers from your 1040.
Social Security Numbers or ITINs for you, your spouse if filing jointly, and all dependents.
Every W-2 and 1099 showing Colorado withholding. Each must be submitted with your return.⁴
Documentation for any subtractions (Schedule DR 0104AD) and credits (DR 0104CR) you plan to claim.

Working Through the Lines

After you enter federal taxable income on Line 1, you move through Colorado’s additions. Line 2 requires you to add back any state income tax you deducted on federal Schedule A; Colorado doesn’t let you deduct the state’s own income tax from itself.⁴ Line 3 is a partial addback of the federal qualified business income deduction under IRC Section 199A, but only if your federal adjusted gross income exceeds $500,000, or $1,000,000 for joint filers.

Subtractions that reduce Colorado taxable income below the federal amount go on Schedule DR 0104AD and transfer onto the main return. Once additions and subtractions are done, you have Colorado taxable income. Tax is calculated on Line 13 by applying the flat 4.4% rate.⁵ Full-year residents can also look up their tax in the table in Book 104.

Claim the TABOR refund on the return itself. For 2025, the refund is a flat credit that varies by filing status and adjusted gross income, ranging from $19 for single filers earning $52,000 or less up to $118 for joint filers earning above $299,001.⁶ Skip the return and you forfeit the refund.

Credits on the DR 0104CR

The Child Care Contribution Credit lets you claim 50% of a qualifying monetary donation to a Colorado child care program, up to $100,000 per year. Attach form DR 1317, the certification from the recipient organization, to your return.⁷ The Enterprise Zone Contribution Credit works similarly: donate to an approved project, receive a tax credit certificate from the project administrator, and submit it with form DR 1366.⁸

Part-Year and Nonresident Filers

If you moved into or out of Colorado during the year, or earned Colorado-source income while living elsewhere, file the DR 0104 with Schedule DR 0104PN attached. The schedule apportions income so Colorado only taxes the portion connected to the state.⁹

You list each category of income (wages, interest, business income, capital gains, and so on) in two columns: a federal column with your total and a Colorado column with only the amount earned while a Colorado resident or from Colorado sources. Divide total Colorado income by total federal income to get an apportionment ratio carried to four decimal places. That ratio multiplied by the tax a full-year resident would owe produces your actual Colorado tax on Line 12 of the DR 0104.

Federal adjustments like the IRA deduction and self-employment tax are also apportioned, generally in the ratio of Colorado wages or self-employment income to the total. Student loan interest uses the broader Colorado-to-federal total income ratio instead. Most part-year errors happen in these ratios, so follow the DR 0104PN instructions adjustment by adjustment.

DR 0100 Sales Tax Returns

Retailers and businesses collecting Colorado sales tax file the DR 0100, the Retail Sales Tax Return. File for every period even if you had zero sales and owe nothing.¹⁰ CDOR assigns your filing frequency (monthly, quarterly, or annual) based on the volume of tax you collect.

Report gross sales, subtract exempt sales and other authorized deductions to reach net taxable sales, then calculate tax due for each jurisdiction where you collect; state, county, city, and special district rates can all stack. Effective January 1, 2026, Colorado eliminated the state service fee that previously let retailers keep a small percentage of collected tax as compensation for timely filing.¹⁰ CDOR posts video walkthroughs on the DR 0100 page for both paper and electronic filing. To correct a previously filed return, file an amended DR 0100 with the full corrected amounts for the period, not just the difference.

Before you can file the DR 0100 or any business tax return, you need a Colorado Account Number assigned during state registration, plus a Federal Employer Identification Number from the IRS. The EIN comes through Form SS-4, and the IRS recommends applying online for the fastest turnaround.¹¹

Submitting Your Return

Revenue Online

Revenue Online is CDOR’s free portal for filing and paying. To create an individual account, request a Letter ID by entering your SSN or ITIN. A letter with your Letter ID is mailed to the address CDOR has on file, which can take up to ten business days.¹² Once you have it, you can log in, file, pay, view account history, and check refund status. Businesses set up accounts using their Colorado Account Number or EIN instead of an SSN, through the same Letter ID process.

Electronic filing generates a confirmation number. Save it as proof of timely submission. E-filed refunds arrive in roughly three to five weeks.¹³ Payments can be made by credit card, debit card, or e-check. Service fees from the payment processor apply to card transactions.¹⁴ The e-check option, drawn directly from your bank account, is typically the cheapest route.

Mailing Paper Returns

Use the correct address based on whether you’re including a payment:

With payment: Colorado Department of Revenue, Denver, CO 80261-0006
Without payment: Colorado Department of Revenue, Denver, CO 80261-0005

Sending to the wrong address can delay processing.¹⁵ Mailed returns must be postmarked by the deadline. Certified mail gives you a delivery receipt if the filing date is ever disputed. Paper returns and paper refund checks can take up to three months to process, far longer than the three-to-five-week electronic timeline.¹³

Deadlines, Extensions, and Estimated Payments

Colorado individual returns and any tax owed are due April 15. Revenue Online accepts electronic returns as timely until midnight; mailed returns must be postmarked by that date.⁴ If you’re traveling or living outside the United States on April 15, your filing deadline shifts to June 15, though interest still runs on any unpaid tax after April 15.

Colorado grants an automatic six-month extension to file, pushing the deadline to October 15, with no form required to claim it.¹⁶ There is no extension to pay. To avoid late-payment penalties, pay at least 90% of your tax liability by April 15, through Revenue Online or by mailing a check with the Extension Payment Form (DR 0158-I). Any remaining balance paid by October 15 will accrue interest but not penalties.

If you have income that isn’t subject to withholding (self-employment earnings, rental income, investment gains) you may need to make quarterly estimated payments using form DR 0104EP. The four due dates are:

First quarter: April 15
Second quarter: June 15
Third quarter: September 15
Fourth quarter: January 15 of the following year

When a due date falls on a weekend or holiday, the deadline moves to the next business day.¹⁷ The DR 0104EP includes a worksheet for calculating each quarter’s payment. Underpaying triggers a separate penalty calculated on form DR 0204, which you’d complete and include with your annual return. Your payment history is visible in Revenue Online.

Fixing Mistakes and Penalties for Late Filing

If you discover an error on a return you already filed, correct it with form DR 0104X, the Amended Colorado Income Tax Return.¹⁸ Fill out the entire return with corrected amounts, not only the lines that changed. CDOR recommends filing the amended return electronically to reduce errors, though you can also mail it. If your federal return was corrected by the IRS, or you filed a federal amended return that changes your Colorado tax, file a Colorado amended return as well. File separately for each year that needs correction.

Colorado imposes separate penalties for filing late and paying late. If both apply, only the larger is assessed. Each starts at the greater of $5 or 5% of the unpaid tax for the first month past the due date, then adds 0.5% for each additional month, capping at 12%.¹⁹ On a $2,000 balance, that’s $100 in the first month and up to $240 if you’re a full year late.

A separate negligence penalty applies when a deficiency results from careless disregard of tax rules: 25% of the deficiency, assessed on top of the tax you already owe.¹⁹ Penalties under C.R.S. 39-22-621 are cumulative, so a late-payment penalty and a negligence penalty can hit the same return. Interest accrues separately on top of penalties, running from the original due date until the balance is paid. Keep records for at least four years after the filing due date, the statute of limitations for CDOR to change your return.⁴

Other Forms Worth Knowing

The DR 0004 is Colorado’s version of the federal W-4, but filing it is optional. Without one, your employer calculates Colorado withholding from your federal W-4 using a method designed to produce a small refund at tax time.²⁰ Use the DR 0004 for more precise withholding, for example if you have significant deductions that would otherwise cause too much to be withheld. Complete a separate DR 0004 for each job if you or your spouse hold multiple positions.

Vehicle title and registration forms are not available through tax.colorado.gov. The DMV side publishes them, including the DR 0024 (sales tax receipt for vehicle purchases), DR 0070 (statement of purchase price), and DR 2009 (transfer of title upon death).² Title transfer documents like the DR 2173 Bill of Sale and DR 2174 Power of Attorney are secure forms that must be purchased from approved vendors; they aren’t free downloads. County motor vehicle offices handle the actual processing.

1
Colorado Department of Revenue – Taxation. Forms in Number Order
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Department of Revenue – Colorado DMV. Forms in Number Order
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Colorado Department of Revenue. DR 0104 – Individual Income Tax Return
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Colorado Department of Revenue – Taxation. Book 104 – Colorado Individual Income Tax Filing Guide
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Colorado Department of Revenue – Taxation. Individual Income Tax – Frequently Asked Questions
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Colorado Department of Revenue – Taxation. TABOR
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Department of Revenue – Taxation. DR 1317 – Child Care Contribution Tax Credit Certification
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Colorado Office of Economic Development and International Trade. Enterprise Zone Contribution Tax Credit
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Colorado Department of Revenue – Taxation. DR 0104PN – Part-Year Resident/Nonresident Tax Calculation
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Colorado Department of Revenue – Taxation. DR 0100 – Retail Sales Tax Return
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Internal Revenue Service. Instructions for Form SS-4
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Colorado Department of Revenue – Taxation. Set Up an Individual Revenue Online Account
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Colorado Department of Revenue – Taxation. Refund
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Colorado Department of Revenue – Taxation. Pay Online by Credit/Debit Card or E-Check
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Colorado Department of Revenue – Taxation. Contact Us By Mail
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Colorado Department of Revenue – Taxation. Individual Income Tax – Due Dates and Filing Extension
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Colorado Department of Revenue – Taxation. Individual Income Tax – Estimated Payments
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Colorado Department of Revenue – Taxation. DR 0104X – Amended Individual Income Tax Return
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Colorado Public Law. Colorado Code 39-22-621 – Interest and Penalties
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Colorado Department of Revenue – Taxation. DR 0004 – Colorado Employee Withholding Certificate