Key Tax Deadlines Every Colorado Resident Should Know in 2026

Last updated: May 2026 | Sources: IRS.gov, Colorado Department of Revenue

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Missing a tax deadline in Colorado can be an expensive mistake. The IRS and the Colorado Department of Revenue both impose penalties and interest on late filings and late payments — and the two sets of deadlines do not always align in ways that are intuitive. Understanding exactly when your federal and state returns are due, when you need to make estimated tax payments, and when extensions kick in can save you hundreds of dollars and a significant amount of stress.

This guide covers every key tax deadline for Colorado individual filers, from the filing season opening date through the end-of-year estimated payment due date. It is based on official IRS and Colorado Department of Revenue guidance current as of May 2026.

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The Colorado Tax Calendar for Individual Filers

January 15, 2026 — Q4 2025 Estimated Tax Payment

If you are self-employed, a freelancer, an independent contractor, or someone with significant income not subject to withholding (such as investment income or rental income), you are likely required to make quarterly estimated tax payments to both the IRS and the Colorado Department of Revenue.

The fourth quarter estimated payment for tax year 2025 was due January 15, 2026. This covers income earned from September 1 through December 31, 2025.

Official source: IRS Publication 505 — Tax Withholding and Estimated Tax

January 26, 2026 — IRS Filing Season Opens

The IRS officially opened the 2026 filing season on January 26, 2026, meaning taxpayers could begin submitting their 2025 federal income tax returns electronically from that date.

Filing as early as possible has several advantages: you receive any refund faster, you reduce the risk of tax-related identity theft (a fraudster cannot file a return in your name if you have already filed), and you avoid the processing backlog that typically builds up as April 15 approaches.

Official source: IRS — 2026 Filing Season Opens

January 31, 2026 — W-2 and 1099 Delivery Deadline

Your employer must furnish your Form W-2 (Wage and Tax Statement) by January 31. Similarly, if you received freelance or contract income, the businesses that paid you must furnish Form 1099-NEC (for non-employee compensation) and most 1099-MISC forms by January 31.

If you have not received your W-2 or 1099 by mid-February, contact the issuing party immediately. You will need these documents before you can file an accurate return.

April 15, 2026 — Federal and Colorado Tax Returns Due

The most important date in the tax calendar. Both your federal Form 1040 and your Colorado Form DR 0104 were due on April 15, 2026 for tax year 2025.

This is also the deadline to:

• Pay any tax you owe without incurring late payment penalties
• Make your first quarter estimated tax payment for 2026 (covering January 1 – March 31)
• Contribute to a traditional IRA or Roth IRA for tax year 2025
• File for an extension if you need more time to file (but not more time to pay)

Colorado flat tax rate: Colorado imposes a flat state income tax rate of 4.40% on taxable income. This rate applies to all income levels, making Colorado's tax structure simpler than most states that use graduated brackets.

Official sources:

• IRS — Filing Deadline
• Colorado Department of Revenue — Individual Income Tax

April 15, 2026 — Q1 2026 Estimated Tax Payment

The same day as the main filing deadline is also when your first estimated tax payment for the current tax year (2026) is due. This covers income earned from January 1 through March 31, 2026.

June 16, 2026 — Q2 2026 Estimated Tax Payment

The second quarterly estimated payment covers income earned from April 1 through May 31, 2026. Note that this deadline falls in June rather than the end of the second quarter — the IRS uses these specific dates rather than calendar quarter end dates.

September 15, 2026 — Q3 2026 Estimated Tax Payment

The third quarterly estimated payment covers income earned from June 1 through August 31, 2026.

October 15, 2026 — Extended Filing Deadline

If you filed for a six-month extension by April 15, your Colorado and federal returns are due by October 15, 2026.

Critical warning: An extension to file is NOT an extension to pay. If you owed tax on April 15 and did not pay it, interest and penalties began accruing from that date regardless of your extension. The extension only gives you more time to submit the paperwork — not more time to send money.

For Colorado specifically, you must have paid at least 90% of your Colorado tax liability by April 15 to avoid underpayment penalties.

Official source: Colorado Extension Payment Form DR 0158-I

January 15, 2027 — Q4 2026 Estimated Tax Payment

The fourth and final estimated payment for tax year 2026 covers income earned from September 1 through December 31, 2026.

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Colorado vs. Federal Deadlines: Key Differences

While Colorado generally follows federal deadlines, there are important differences Colorado filers must understand.

Colorado does not conform to all federal deductions

Colorado's tax code does not automatically adopt every federal deduction or credit. For 2026, a particularly important difference is the Overtime Compensation Deduction Addback. The federal government introduced a deduction for qualified overtime compensation in 2026 (via P.L. 119-21). Colorado, however, requires taxpayers to add this deduction back on their Colorado return — meaning the overtime deduction only reduces your federal tax, not your Colorado tax.

Official source: Colorado HB 25-1296 — Overtime Compensation Deduction Addback

Colorado has no estate or inheritance tax

Unlike many states, Colorado imposes no state-level estate tax or inheritance tax. This can simplify end-of-year planning for estates and beneficiaries.

TABOR refunds

Colorado's Taxpayer's Bill of Rights (TABOR), enacted in 1992, limits annual state revenue growth. When revenue exceeds the TABOR cap, the state must refund the surplus to taxpayers. TABOR refunds are distributed to all Colorado individual income tax filers and can represent meaningful money — check your Colorado DR 0104 instructions each year to see if a TABOR refund applies.

The FAMLI program

Colorado's Family and Medical Leave Insurance (FAMLI) program requires both employer and employee contributions through payroll. Employee contributions are reported in Box 14a of your W-2 and are not deductible on your Colorado return. FAMLI benefits you receive are taxable income at the federal level.

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What Happens If You Miss the Deadline?

Late filing penalty

The IRS imposes a failure-to-file penalty of 5% of unpaid tax per month, up to a maximum of 25% of unpaid tax. Colorado similarly imposes penalties for late filing.

Late payment penalty

Separate from the filing penalty, the IRS imposes a failure-to-pay penalty of 0.5% of unpaid tax per month, up to 25%.

Interest

Both the IRS and Colorado charge interest on unpaid balances from the original due date until payment is received. Interest is not waived even if you have an extension.

The good news: penalty abatement

If you have a clean compliance history, you may qualify for first-time penalty abatement from the IRS. This allows the IRS to waive certain penalties for taxpayers who have no history of penalties in the prior three years. Contact the IRS or a licensed CPA to explore this option.

Official source: IRS Penalty Relief — First Time Abatement

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Estimated Taxes: Who Needs to Pay and How Much?

Estimated taxes are quarterly payments made by taxpayers whose income is not subject to withholding — primarily the self-employed, freelancers, independent contractors, investors, and landlords.

You generally need to make estimated tax payments if you expect to owe at least $1,000 in federal tax after subtracting withholding and credits. For Colorado, the threshold is similar — you must make estimated payments if you expect to owe a significant amount in Colorado income tax after subtracting withholding and credits.

Colorado requires you to have paid at least 90% of your current year tax liability or 100% of the prior year's tax liability by the filing deadline to avoid underpayment penalties.

2026 Estimated Tax Due Dates

How to pay: Federal estimated payments can be made through the IRS Direct Pay system at IRS.gov/payments or via EFTPS (Electronic Federal Tax Payment System). Colorado estimated payments can be made through Revenue Online at colorado.gov/revenueonline.

Official source: IRS Form 1040-ES — Estimated Tax for Individuals

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Free Filing Options for Colorado Residents

Colorado residents have several options for filing their tax returns at no cost.

IRS Free File

If your adjusted gross income (AGI) is $84,000 or less, you can file your federal return for free using one of the IRS Free File software partners at IRS.gov/freefile. Some partners also offer free state filing.

VITA — Volunteer Income Tax Assistance

VITA sites across Colorado offer free in-person tax preparation help to individuals who earn $69,000 or less, have disabilities, or have limited English proficiency. Sites are staffed by IRS-certified volunteers.

TCE — Tax Counseling for the Elderly

The TCE program, also operated with IRS support, provides free tax help to individuals 60 and older. TCE specializes in questions about pensions, retirement-related issues, and Social Security income.

AARP Tax-Aide

AARP Tax-Aide, available at hundreds of locations across Colorado, offers free tax preparation help to taxpayers of all ages, though it focuses on seniors.

Find Colorado VITA/TCE sites: Get Ahead Colorado — File Your Taxes

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When Is a CPA Worth It?

Tax software handles the filing process well for most straightforward situations. A licensed Colorado CPA becomes especially valuable when:

• You are self-employed and unsure about estimated tax requirements
• You have income from multiple states
• You experienced a major life event (marriage, divorce, inheritance, home purchase, job loss)
• You have investment income, rental income, or stock options
• You missed a deadline and need help with penalty abatement
• You received a notice from the IRS or Colorado Department of Revenue
• You want to understand how Colorado's 2026 tax changes (overtime addback, FAMLI, TABOR) affect your specific situation

A CPA can also help you plan proactively — setting up estimated payments correctly at the start of the year so you avoid underpayment penalties entirely.

Find a licensed Colorado CPA: ColoradoAccountants.com

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Quick Reference: 2026 Colorado Tax Calendar

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Official Resources

• IRS Filing Deadline Information
• IRS Estimated Tax — Form 1040-ES
• Colorado Department of Revenue — Individual Income Tax
• Colorado Revenue Online — Make a Payment
• IRS Free File
• Get Ahead Colorado — Free Tax Filing Resources
• Colorado FAMLI Program

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This article is for informational purposes only and does not constitute tax advice. Tax laws change frequently. For advice specific to your situation, consult a licensed Colorado CPA.

Find a licensed Colorado CPA near you →