1099 Quarterly Taxes in Colorado (2025-2026)
If you're self-employed in Colorado — freelancer, contractor, gig worker, or single-member LLC — you owe quarterly estimated taxes to two agencies: the IRS (federal) and Colorado Department of Revenue (state). Colorado uses a flat 4.40% income tax, which makes estimating your state burden simpler than progressive states. But you still need to send the money on time to avoid underpayment penalties.
Colorado state income tax (2025)
Colorado uses a flat income tax rate of 4.40% on all taxable income above the standard deduction. There are no brackets — every dollar of taxable income is taxed at the same rate.
How to pay Colorado estimated taxes
Federal estimated tax due dates (April 15, June 16, September 15, 2026, and January 15, 2027) apply to your Colorado state estimated payments as well — most states piggyback on the federal schedule. Pay Colorado taxes through the Colorado Department of Revenue's online portal: www.colorado.gov/revenueonline. You can also mail Form 104EP with a check.
Colorado-specific quirk freelancers miss
Colorado's flat 4.4% rate is uniform regardless of income. The state issued TABOR refunds in recent years that reduced effective rates further. Self-employed Coloradans should also check if they need to register for state sales tax (state-collected vs home-rule cities can be tricky).
Common deductions for Colorado freelancers
- Colorado allows the same business expenses (home office, mileage, software, etc.) as federal.
- Half of SE tax is deductible federally; check Colorado's rules for state conformity.
- CO conforms to federal QBI deduction starting from federal taxable income.
- SEP-IRA / Solo 401(k) contributions reduce both federal and Colorado taxable income.
- Self-employed health insurance premiums are deductible federally.