How to Complete and File the Colorado DR 0104 Income Tax Return

The Colorado DR 0104 is the state’s individual income tax return, and it builds directly off your finished federal 1040. Colorado applies a flat 4.4 percent tax to your federal taxable income after state-level adjustments, so you calculate federal first and then work through the DR 0104 to arrive at what you owe Colorado or what Colorado owes you.¹ Returns are due April 15. You can file for free through the state’s Revenue Online portal or mail a paper copy to the Department of Revenue in Denver.²

Who Has to File

You need to file a DR 0104 if you were required to file a federal return and you have any Colorado income tax liability for the year. That applies whether you lived in Colorado the whole year or only earned money from Colorado sources while living elsewhere.³

Full-year residents report all income regardless of where it was earned. Part-year residents and nonresidents owe Colorado tax only on income from Colorado sources, but they still complete the full DR 0104 as if they were full-year residents and then prorate the tax on a schedule called the DR 0104PN.⁴ Your Colorado filing status must match your federal filing status. If you filed jointly with the IRS, you file jointly with Colorado.¹

What to Have in Front of You

Because the DR 0104 pulls numbers directly from your 1040, finish the federal return first. Then pull together:

Your completed federal 1040. You’ll need federal taxable income from line 15 and federal adjusted gross income from line 11.⁵
Social Security numbers or ITINs for you, your spouse if filing jointly, and every dependent.
Your Colorado driver’s license or state ID. The form asks for the ID number, issuing state, issue date, and expiration date.⁵
W-2s and 1099s showing Colorado withholding. These must be submitted with your return. Paper filers staple them to the front; electronic filers attach scans.⁶
Records of any quarterly estimated payments you made during the year.
Documentation for anything you plan to subtract or claim as a credit — pension statements, 529 contribution records, child care receipts, and so on.

Working Through the Form

The DR 0104 runs eight pages, but the core calculation sits on the first two.

Personal Information and Dependents

Pages one and two collect your name, address, Social Security number, driver’s license details, and dependents. For each dependent, check the box if they qualify for the Colorado Child Tax Credit.⁵ Names and Social Security numbers have to match your federal return exactly; mismatches cause processing delays.

Income and Tax Calculation

Line 1 is your federal taxable income, straight from 1040 line 15. Line 4 adds any Colorado-specific additions and line 10 subtracts any Colorado subtractions, both drawn from the DR 0104AD schedule. What’s left is your Colorado taxable income.

The flat 4.4 percent rate is applied to that number.⁷ The form then reduces the result by any nonrefundable credits on line 16 (from the DR 0104CR) to arrive at your net tax.

Payments, Refund, or Balance Due

The lower portion of the form tallies what you’ve already paid: employer withholding on line 21, estimated payments on line 22, and refundable credits on line 28 (also from the DR 0104CR). Subtract those from your net tax. If payments exceed the tax, you have a refund. If the tax exceeds payments, you owe. Line 31 asks for your federal adjusted gross income, which the Department uses to verify the return.⁵

The Supporting Schedules

The DR 0104 itself is mostly a summary. The detail lives in three schedules you attach when they apply.

DR 0104AD: Subtractions From Income

This schedule lists every adjustment that can drop your Colorado taxable income below your federal taxable income. The subtractions most individual filers use include:⁸

State tax refunds you reported as income on your federal return can be subtracted back out.
Interest from U.S. Treasury bonds and similar federal instruments is exempt from state tax.
Social Security and SSDI income included in your federal taxable income can be subtracted.
Pension and annuity income is deductible up to $20,000 for taxpayers under 65 and up to $24,000 for those 65 and older.⁹
CollegeInvest 529 contributions are deductible. For the 2026 tax year, single filers can subtract up to $26,200 per beneficiary, and joint filers up to $39,200 per beneficiary.
FAMLI paid family and medical leave benefits included in your federal income can be subtracted.

You have to attach the completed DR 0104AD if you claim any subtractions.⁵

DR 0104CR: Individual Credit Schedule

This schedule calculates both refundable and nonrefundable credits. The ones most individual filers encounter are the Colorado Child Tax Credit, the Child and Dependent Care Expenses Credit, and the Colorado Earned Income Tax Credit.¹⁰ Refundable credits from Part I flow to line 28 of the DR 0104; nonrefundable credits from Part III flow to line 16.

If you paid income tax to another state on income Colorado also taxes, Part II of the DR 0104CR carries a credit for tax paid to another state. This generally applies to full-year Colorado residents who earned income elsewhere. Nonresidents and most part-year residents don’t qualify.¹⁰

DR 0104PN: Part-Year and Nonresident Schedule

Part-year residents and nonresidents use this schedule to isolate the portion of their income attributable to Colorado. Complete the DR 0104 as though you were a full-year resident, then use the DR 0104PN to prorate the tax based on Colorado-source income. The prorated figure replaces the full-year calculation.⁴

Submitting the Return

Filing Online

The Department of Revenue offers free electronic filing through Revenue Online. You don’t need to create an account to file. The system lets you submit as a guest and set up a login later if you want to view your account.¹¹ Electronic filing cuts down on errors and processes faster than paper.

Filing on Paper

Paper filers send all eight pages. The mailing address depends on whether a payment is enclosed:¹²

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

Staple your W-2s and 1099s showing Colorado withholding to the front of the return where indicated.⁶ Certified mail or a trackable service gives you proof of delivery if a timing question ever comes up.

Deadline and Extensions

Individual returns are due April 15 of the year after the tax year. For the 2026 tax year, that’s April 15, 2027.²

If you can’t finish by April 15, Colorado grants an automatic six-month extension to file, moving your deadline to October 15. You don’t submit a separate extension request unless you owe tax. If you do owe, use Form DR 0158-I to send an estimated payment by the original April 15 deadline.¹³ The extension gives you more time to file, not more time to pay. Interest and penalties start accruing on unpaid balances after April 15.

After You File

Refund Timing

Electronic returns generally produce refunds in three to five weeks. Paper returns take up to three months. You can track your refund status through Revenue Online, which shows the same information Department staff see. The tool updates regularly, so checking it is more productive than calling.¹⁴

Notices of Deficiency

If the Department reviews your return and finds a discrepancy — an unreported income source, a subtraction you didn’t qualify for, a math error — it will mail a Notice of Deficiency for the additional tax it believes you owe.¹⁵ You have 30 days from the mailing date to respond. If you disagree, you can file a written protest that includes a copy of the notice, the amounts in dispute, and a statement of why you believe the tax isn’t due. You can also request a hearing with the Executive Director within that same 30-day window. The Department cannot extend that deadline.¹⁶

Ignoring a notice doesn’t make it go away. If you don’t respond within 30 days, the assessed amount becomes final and moves to collections.

If You File or Pay Late

Late filing and late payment trigger separate penalties. The income tax penalty is the greater of $5 or 5 percent of the unpaid tax, plus an additional half-percent for each full or partial month the tax stays unpaid. The total penalty is capped at 12 percent.¹⁷

Interest runs on top of penalties. For 2026, Colorado charges 11 percent annual interest on unpaid balances at the regular rate, or 8 percent for taxpayers who qualify for the discounted rate.¹⁷ Both penalties and interest run from the original due date, not from when you eventually file, so even short delays add up if the balance is meaningful.

Fixing a Mistake After You File

If you find an error on a return you already filed, or the IRS adjusts your federal return in a way that changes your Colorado tax, file an amended return on Form DR 0104X. Fill it out with the corrected amounts, not just the changes. You can submit it electronically through Revenue Online or mail a paper copy.¹⁸

Colorado’s assessment period is tied to the federal statute of limitations plus one additional year. In practice, the Department can generally review and adjust your return for about four years after filing. Filing an amendment sooner rather than later stops interest from accruing on any additional tax you owe and preserves your right to a refund if the correction runs the other way.

1
Department of Revenue – Taxation. Individual Income Tax – Frequently Asked Questions
2
Department of Revenue – Taxation. Colorado Taxes and Fees Due Date Guide
3
Justia. Colorado Code 39-22-601 – Returns
4
Department of Revenue – Taxation. Part-Year and Nonresident
5
Colorado Department of Revenue. 2024 Colorado Individual Income Tax Return
6
Department of Revenue – Taxation. Individual Wage Withholding, W-2 and 1099 Statements
7
Colorado General Assembly. Individual Income Tax
8
Colorado Department of Revenue. DR 0104AD – 2025 Subtractions From Income Schedule
9
Department of Revenue – Taxation. Individual Income Tax – Information for Retirees
10
Colorado Department of Revenue. DR 0104CR – 2025 Individual Credit Schedule
11
Department of Revenue – Taxation. File Individual Income Tax Online
12
Colorado Department of Revenue. DR 0104 – 2025 Colorado Individual Income Tax Return
13
Department of Revenue – Taxation. DR 0158-I – Extension Payment for Colorado Individual Income Tax
14
Department of Revenue – Taxation. Refund
15
Department of Revenue – Taxation. Collections
16
Department of Revenue – Taxation. Protest Rights and Process
17
Department of Revenue – Taxation. Tax Topics – Penalties and Interest
18
Department of Revenue – Taxation. DR 0104X – Amended Individual Income Tax Return