State Tax Calendar
Colorado 2025 Tax Deadline Calendar
Complete filing deadlines for Colorado individual, S-Corp, partnership, and corporate returns — including state-specific forms and rules.
How Colorado Differs from Federal
- →Flat 4.4% income tax rate — Colorado uses a flat rate for both individuals and corporations, effective 2023.
- →Extension payment required — File Form DR 0158-I and pay any balance due by April 15 to get an automatic extension to October 15. The federal extension alone does not extend Colorado.
- →S-Corp / Partnership returns (Form DR 0106) due March 15, with extension to September 15. Partners/shareholders must also file individual Colorado returns.
- →Estimated tax quarters differ slightly — Colorado Q2 estimated tax is due June 15 (not June 16 as federal).
2025 Colorado Filing Calendar
| Date | Filing / Payment Type | Entity Type | Notes |
|---|---|---|---|
| Jan 15 | Q4 2024 Estimated Tax (DR 0104EP) | Individuals / Sole Props | Same as federal |
| Jan 31 | W-2 / 1099-NEC to State | All Employers | File with Colorado DOR |
| Mar 15 | S-Corp / Partnership Return (Form DR 0106) | S-Corps / Partnerships | Extension to Sep 15 |
| Apr 15 | Individual Income Tax (Form DR 0104) | Individuals | Extension to Oct 15 (DR 0158-I required if balance due) |
| Apr 15 | C-Corp Return (Form DR 0112) | C-Corporations | Extension to Oct 15 (DR 0158-C required if balance due) |
| Apr 15 | Q1 2025 Estimated Tax (DR 0104EP) | Individuals / Sole Props | Same as federal |
| Apr 15 | Extension Payment (Form DR 0158-I) | Individuals needing extension | Pay balance due to get Oct 15 extension |
| Jun 15 | Q2 2025 Estimated Tax (DR 0104EP) | Individuals / Sole Props | Colorado Q2 is Jun 15 (not Jun 16) |
| Sep 15 | Q3 2025 Estimated Tax (DR 0104EP) | Individuals / Sole Props | Same as federal |
| Sep 15 | Extended S-Corp / Partnership Returns | S-Corps / Partnerships | Final — no further extension |
| Oct 15 | Extended Individual Return (DR 0104) | Individuals | Final deadline |
| Oct 15 | Extended C-Corp Return (DR 0112) | C-Corporations | Final deadline |
| Jan 15, 2026 | Q4 2025 Estimated Tax | Individuals / Sole Props | Same as federal |
Colorado-Specific Tax Rules
Extension Payment is Mandatory
Unlike Montana, Colorado requires you to pay any balance due with Form DR 0158-I by April 15 to receive an extension. Filing a federal extension alone does not extend your Colorado deadline.
Flat 4.4% Income Tax
Colorado's flat income tax rate of 4.4% applies to all taxable income for both individuals and corporations. This is one of the lower flat rates in the country.
Sales Tax Complexity
Colorado has one of the most complex sales tax systems in the US — state (2.9%), county, city, and special district taxes stack. Rates vary by delivery address and can exceed 10% in some jurisdictions.
Non-Resident Withholding
Colorado requires 4.4% withholding on distributions to non-resident partners and S-Corp shareholders unless they file a Colorado return or composite return.
Federal vs. Colorado — Quick Comparison
| Filing Type | Federal | Colorado |
|---|---|---|
| Individual Return | April 15 | April 15 (same) |
| S-Corp / Partnership Return | March 15 | March 15 (same) |
| C-Corp Return | April 15 | April 15 (same) |
| Individual Extension | October 15 | October 15 (DR 0158-I required if balance due) |
| S-Corp Extension | September 15 | September 15 (same) |
| Q2 Estimated Tax | June 16 | June 15 (one day earlier) |
| W-2 / 1099-NEC to State | January 31 | January 31 (same) |
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