Colorado grants automatic extensions to every filer but diverges from the federal calendar on two business deadlines: the corporate return moved to May, and pass-throughs file in April, not on the federal March date. The state’s flat rate also snapped back for 2025.
Colorado Tax Deadlines at a Glance (2026)
Entity Type | Return Due | Extended Due Date |
|---|---|---|
Individuals (DR 0104) | April 15, 2026 | October 15, 2026 |
C Corporations (DR 0112) | May 15, 2026 | November 15, 2026 |
S Corporations (DR 0106) | April 15, 2026 | October 15, 2026 |
Partnerships (DR 0106) | April 15, 2026 | October 15, 2026 |
Two corrections CPAs should note. The C-corporation DR 0112 is due May 15, 2026 — the 15th day of the 5th month, a change effective for tax years beginning in 2024 — not April 15. And the DR 0106 pass-through return is due April 15, 2026, not the federal March 16; Colorado uses the 4th-month rule. All extensions are automatic with no form; pay at least 90% by the original date.
The Flat Rate Returned to 4.40%
Colorado’s flat individual income tax rate is 4.40% for the 2025 tax year. The 4.25% many taxpayers saw was a 2024-only temporary reduction tied to a TABOR surplus; the statutory 4.40% rate applies for 2025. The corporate rate is also 4.40%.
SALT Parity PTE Election
Under the SALT Parity Act, partnerships and S corporations may elect to pay a 4.40% entity-level tax (on Form DR 0106 or pre-filed via DR 1705), giving owners a credit — a federal SALT-cap workaround. The election is active for the 2025 tax year; note the statute currently sunsets for years beginning on or after January 1, 2026, so confirm renewal before relying on it for 2026.
Home-Rule Cities, Estimates, and Penalties
Colorado has 70+ self-collecting home-rule municipalities, each with its own sales-tax rates, rules, and deadlines, filed directly with the city (the state’s SUTS portal offers single-point remittance for participants). Individual estimated payments are due April 15, June 15, September 15, 2026, and January 15, 2027. Extensions cover filing only — an extension is not an extension to pay.
CPA Action Steps
Use May 15 for the C-corp DR 0112 — not April 15
File DR 0106 pass-through returns in April, not on the federal March date
Apply 4.40% for 2025 (the 4.25% rate was 2024-only)
Track home-rule city obligations separately
Verify current rates and dates against the Colorado Department of Revenue (tax.colorado.gov) before filing.