How to File Colorado State Taxes: Forms, Deadlines, and Extensions

To file your Colorado state taxes, complete Form DR 0104, which starts with your federal taxable income, applies Colorado-specific subtractions and credits, and taxes the result at a flat 4.4% for tax year 2025.¹ The return and any payment are due April 15, 2026. You can file electronically through the state’s free Revenue Online portal or mail a paper return.

Do You Need to File

You need to file a Colorado return if you were a full-year resident, a part-year resident with taxable income during your Colorado months, or a nonresident with income from Colorado sources, and you either had to file a federal return or owe Colorado tax for the year.²

File even when you expect a refund. The TABOR sales tax refund only reaches you through a filed return, and if the Department of Revenue thinks you should have filed and didn’t, it can prepare a return for you using whatever information it has, usually without the deductions and credits that would lower your bill.²

Pick the Right Forms for Your Residency

Residency decides which schedules travel with your DR 0104 and how much of your income Colorado can tax.

Full-year residents were domiciled in Colorado all year, or kept a permanent place of abode here and spent more than six months in the state. They report income from every source.³
Part-year residents moved in or out during the year. They file DR 0104 with Form DR 0104PN to tax only income earned while in Colorado or from Colorado sources.⁴
Nonresidents who never lived in Colorado but earned income here (wages for work performed in the state, rental income from Colorado property) also file DR 0104 with DR 0104PN to isolate the Colorado-source portion.⁴

If you split time between Colorado and another state, the six-month threshold and whether you kept a permanent home here are what matter.

What to Gather Before You Start

Because Colorado’s calculation begins with your federal taxable income, finish or nearly finish your federal return first.⁵ Then pull together:

W-2s and 1099s showing income and any Colorado withholding.
Social Security or ITIN numbers for you, your spouse if filing jointly, and all dependents.
Dates and amounts of any estimated payments you made during the year.
Documentation for Colorado subtractions and credits you plan to claim: 529 contribution records, pension or 1099-R statements, child tax credit information, and similar backup.

Download Form DR 0104 and the full filing booklet from the Department of Revenue website. The booklet bundles the common schedules: DR 0104AD (subtractions), DR 0104CR (credits), DR 0104PN (part-year/nonresident), DR 0104CH (voluntary contributions), and the DR 0900 payment voucher.⁶

Working Through Form DR 0104

Colorado has no brackets, which keeps the arithmetic simple. Start with federal taxable income from your federal Form 1040. Apply Colorado additions and subtractions to arrive at Colorado taxable income. Multiply by 4.4% for tax year 2025 to get your base tax.¹

From that base tax, subtract any credits you qualify for and then what you’ve already paid through withholding and estimated payments. The remainder is your refund or your balance due. The return also has a line for use tax on purchases where no Colorado sales tax was collected, typically from out-of-state online sellers. If you want to direct part of a refund to a state-supported fund like the Colorado Cancer Fund or the Homeless Prevention Fund, use Form DR 0104CH; those contributions reduce your refund or add to your balance.

Colorado Subtractions and Credits Most Filers Use

Report subtractions on Form DR 0104AD. Commonly claimed items include:⁷

Prior-year Colorado state tax refunds that showed up as income on your federal return.
Social Security benefits included in federal taxable income.
Qualifying pension, annuity, IRA, and disability income (separate from Social Security).
Military retirement benefits, reported on their own line with 1099-R copies attached.
CollegeInvest 529 contributions, up to $25,400 per beneficiary for single filers or $38,100 per beneficiary for joint filers in tax year 2025.⁸
Interest on U.S. Treasury bonds and similar federal obligations that was taxed federally.

The most common addition is interest from other states’ municipal bonds that you excluded on your federal return. Colorado adds it back.

Child Tax Credit

Colorado’s child tax credit covers children under age 6 at year-end. For tax year 2025 it ranges from $200 to $1,200 per eligible child by income: single filers with AGI up to $26,000 get the full $1,200, and the credit drops to $200 for AGI between $51,001 and $77,000. Joint filers follow the same tiered structure with slightly higher thresholds, phasing out at $87,000. A separate family affordability tax credit applies to children under 17, and for children under 6 the two stack, adding up to $3,273 per child at the lowest incomes. The combined credits phase out above $85,000 for single filers and $96,000 for joint filers.⁹

TABOR Refund

For tax year 2025, the TABOR refund is a sales tax refund that varies by income: $19 to $59 for single filers and $38 to $118 for joint filers. It’s claimed on your state income tax return and combined with any regular refund, not sent separately.¹⁰

How to Submit the Return

Revenue Online, the Department of Revenue’s free portal, lets you file electronically without buying tax software or creating an account, though you can set an account up afterward to track your return.¹¹ Save or print the confirmation as proof of timely filing. E-filed refunds typically arrive within three to five weeks; paper returns can take up to three months.¹²

If you mail a paper return, the address depends on whether a payment is enclosed. Returns with a payment go to Colorado Department of Revenue, Denver, CO 80261-0006. Returns without a payment go to Denver, CO 80261-0005.¹³

Deadline, Extension, and Paying What You Owe

The return and any tax owed are due April 15 of the year following the tax year, shifting to the next business day if that date falls on a weekend or legal holiday.¹⁴ For the 2025 tax year, that’s April 15, 2026.

Colorado grants an automatic six-month extension to file, pushing the paperwork deadline to October 15. The extension does not extend time to pay. Any tax owed is still due April 15, and penalties and interest start running the day after.¹⁵ If you need the extra filing time but expect to owe, send a payment with Form DR 0158-I by April 15 or pay through Revenue Online.

Pay a balance due through Revenue Online by electronic funds transfer or credit card (credit cards carry a convenience fee of roughly 2.2% to 2.3%). To pay by check or money order, include Form DR 0900 so the payment reaches the right account and tax year, and mail it to Colorado Department of Revenue, Denver, CO 80261-0008.¹³

If you can’t pay in full, the Department of Revenue offers monthly payment plans with no setup fee, though penalties and interest keep accruing and any future refunds get applied to the balance. For current-year tax debt, you must wait until after April 15 and call the Collections Section at (303) 205-8291; for prior-year bills you’ve already received, you can set the plan up in Revenue Online. Missing a payment or falling behind on later filings voids the agreement.¹⁶

If You File or Pay Late

Colorado charges a single combined penalty of 5% of the unpaid tax plus 0.5% for each month or partial month the tax remains unpaid, capped at 12%, with a $5 minimum.¹⁷ Interest also accrues from the original due date, at a discounted 8% for 2026 if you pay before the Department issues a notice of deficiency or within 30 days of receiving one, and 11% otherwise.¹⁸ Because the penalty is a percentage of unpaid tax, paying most of your estimated balance by April 15 (even if you file later under extension) sharply limits what you’ll owe on top.

Fixing a Mistake After You File

Use Form DR 0104X to amend a return, matching the version to the tax year you’re correcting. Fill in the corrected figures and attach all supporting schedules and documentation, including items that didn’t change. Part-year residents and nonresidents attach a corrected DR 0104PN. You can file the DR 0104X in Revenue Online or by mail, using the same address split as original returns: Denver, CO 80261-0006 with payment, Denver, CO 80261-0005 without.¹⁹

1
Department of Revenue – Taxation. Individual Income Tax Guide
2
Department of Revenue – Taxation. Individual Income Tax Filing Requirements
3
Cornell Law School. Colorado Regulation 39-22-103(8)(a) – Resident Individual
4
Department of Revenue – Taxation. Part-Year and Nonresident
5
Justia. Colorado Revised Statutes Section 39-22-104 – Income Tax Imposed on Individuals, Estates, and Trusts
6
Department of Revenue – Taxation. DR 0104 Booklet – Individual Income Tax Filing Booklet
7
Colorado Department of Revenue. DR 0104AD – 2025 Subtractions from Income Schedule
8
Department of Revenue – Taxation. Income Tax Topics: CollegeInvest Contribution Subtraction
9
Colorado Department of Revenue. DR 0104CN – 2025 Colorado Child Tax Credit
10
Department of Revenue – Taxation. TABOR
11
Department of Revenue – Taxation. File Individual Income Tax Online
12
Department of Revenue – Taxation. Refund
13
Department of Revenue – Taxation. Contact Us By Mail
14
Department of Revenue – Taxation. Colorado Taxes and Fees Due Date Guide
15
Colorado Department of Revenue. Extension Payment for Colorado Individual Income Tax Instructions
16
Department of Revenue – Taxation. Payment Plans
17
Justia. Colorado Revised Statutes Section 39-22-621 – Penalties
18
Colorado Department of Revenue. Tax Topics: Penalties and Interest
19
Colorado Department of Revenue. DR 0104X – Amended Individual Income Return Instructions