If you earn 1099 or self-employment income in Colorado, the IRS and the state both expect you to pay taxes as you go — in four quarterly installments rather than one April bill. This calculator estimates your 2026 quarterly payments across all three pieces: federal self-employment tax, federal income tax, and Colorado state income tax. Colorado has a flat 4.4% income tax, so your effective state rate is the same at every income level. Enter your expected net self-employment income, any W-2 wages, and your filing status to see what to send each quarter, your due dates, and how the safe-harbor rules protect you from an underpayment penalty. Everything is an estimate for planning — always confirm with the Colorado Department of Revenue before you file.
Self-employment income has no tax withheld for you, so both the IRS and Colorado Department of Revenue ask you to prepay in quarterly installments. On the federal side you owe self-employment tax (15.3% Social Security and Medicare on 92.35% of your net profit, up to the Social Security wage base) plus federal income tax on your profit after the standard deduction. On top of that, Colorado applies its own income tax.
Colorado generally requires estimated payments once you expect to owe more than $1,000 in state tax for the year. Colorado follows the federal schedule: April 15, June 15, September 15, and January 15. Colorado follows the standard four-installment schedule.
You avoid an IRS underpayment penalty by hitting a "safe harbor": paying at least 90% of this year's total tax, or 100% of last year's (110% if your income is higher). Colorado starts from your federal taxable income and applies a flat 4.4% rate, so the federal standard deduction and the deductible half of self-employment tax are already reflected before the state rate. You can pay online through the Colorado Department of Revenue portal, and the calculator above breaks your total into the federal and Colorado pieces so you can send each to the right place. You can pay online at the Colorado Department of Revenue (payment portal).
For educational purposes only — not tax advice. Tax rules change and individual situations vary; confirm figures with a tax professional and the Colorado Department of Revenue before filing. State tax data last verified 2026-07-05.
Sources: tax.colorado.gov, tax.colorado.gov.