2026 Colorado State Tax Deadlines
Colorado Individual income tax filing deadlines and extensions for 2026
If you are a resident or have been involved in business operations within Colorado, you might be required to file Colorado State taxes. Colorado follows a flat income tax structure with a 4.25% rate, making it essential to understand the specific deadlines and requirements for 2026.
Colorado business tax deadlines for 2026
C Corporations' deadlines and requirements
C Corporations in Colorado must file and pay Corporate Income Taxes by April 15, 2027, following the federal due date schedule.
Filing requirements include:
- Complete Form DR 0112 (Colorado Corporate Income Tax Return)
- File via Revenue Online
- Payment must be made by April 15, 2027
- Mail submissions must be postmarked by the due date
Extension to file taxes in Colorado for 2026
The Extension Deadline for Colorado Corporate income tax returns is October 15, 2027. Colorado automatically grants a six-month extension to file; payment is still due April 15, 2027.
Pass-through entities
Colorado S Corporations and Partnerships tax deadlines for 2026
S Corporations and Partnerships must file in Colorado by April 15, 2027.
Required forms include:
- Form DR 0113—S Corporation Return
- Form DR 0115—Partnership Return
Extension to file S Corporations and Partnerships taxes in Colorado for 2026
The Extension Deadline for Colorado S Corporations and Partnerships returns is October 15, 2027. Colorado automatically grants a six-month extension without requiring separate applications. This is an extension to FILE, not an extension to PAY—payment is still due April 15, 2027.
Colorado Individual tax considerations for 2026
Filing requirements and income thresholds
Colorado Individuals must file a State income tax return if their gross income exceeds specific thresholds based on filing status.
The flat tax rate for 2026 is:
- 4.25% on all Colorado taxable income
Estimated tax deadline for Colorado 2026
Estimated tax payments are due on the following schedule for calendar year filers:
- April 15, 2026
- June 15, 2026
- September 15, 2026
- January 15, 2027
Who must make estimated payments
You must make Colorado estimated income tax payments during 2026 if you expect to owe a significant amount in Colorado income tax after subtracting withholding and credits. Colorado requires 90% payment to avoid underpayment penalties. Electronic payments are encouraged through the Colorado online tax system.
Individual tax deadline for Colorado 2026
Individual income tax returns are due April 15, 2027.
Available forms include:
- Form DR 0104—Colorado Individual Income Tax Return
Extension to file taxes in Colorado for 2026
The Extension Deadline is October 15, 2027, to file your Colorado Individual Income tax return. Colorado automatically grants a six-month extension without requiring separate extension forms. This is an extension to FILE, not an extension to PAY—payment is still due April 15, 2027.
What Colorado tax professionals need to know
Several key considerations make Colorado's tax landscape unique for 2026. Colorado's flat income tax system provides simplicity and predictability for taxpayers and tax professionals. Electronic filing requirements continue to expand, and Colorado offers various tax planning opportunities.
Electronic filing requirements
Colorado has implemented electronic filing systems for taxpayers:
- C Corporations and pass-through entities should file electronically through Revenue Online
- Individuals can use Colorado's online system for free electronic filing
- Business deductions can be processed more efficiently through electronic systems
- Professional preparers must use approved software vendors
Colorado's unique tax features for 2026
4.25% flat rate on all Colorado taxable income
Colorado's flat tax structure provides simplicity and predictability for all taxpayers.
90% payment requirement to avoid underpayment penalties
Colorado requires taxpayers to pay 90% of their estimated tax liability to avoid penalties.
TABOR and Revenue Limitations
Colorado's Taxpayer Bill of Rights (TABOR) creates unique considerations:
- Constitutional revenue limitations may trigger refunds to taxpayers
- TABOR refunds are distributed when state revenues exceed limits
- Tax planning must consider potential refund mechanisms
- Multi-year planning is affected by revenue limitations
Business incentives and credits
Colorado provides various business tax incentives:
- Enterprise zone credits for qualifying businesses
- Job growth incentive tax credits
- Research and development credits
- Advanced industry investment tax credits
Retirement income considerations
Colorado provides certain retirement income benefits:
- Military retirement pay exemptions may apply
- Social Security benefits treatment
- Pension income considerations for residents
Professional tax guidance
For complex Colorado tax situations, consulting with qualified tax professionals through an accounting firm directory can help ensure compliance and identify available tax-saving opportunities.
Sources
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The material discussed on this page is meant for general illustration and/or informational purposes only and is not to be construed as investment, tax, or legal advice. You must exercise your own independent professional judgment, recognizing that advice should not be based on unreasonable factual or legal assumptions or unreasonably rely upon representations of the client or others. Further, any advice you provide in connection with tax return preparation must comply in full with the requirements of IRS Circular 230.
Please note that if any due date falls on a federal or state holiday or weekend, it may be adjusted to the next business day. Always verify current deadlines with the appropriate tax professional and authorities.
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