Colorado Quarterly Tax Calculator
Calculate your estimated quarterly tax payments for federal and Colorado state taxes. Designed for self-employed individuals, freelancers, and independent contractors.
CO State Tax: Flat 4.4%
Quarterly Payment Amount
$6,411
Per quarter (4 remaining)
Annual Tax Breakdown
2026 Payment Schedule
Jan 1 - Mar 31
Due: April 15, 2026
$6,411
Apr 1 - May 31
Due: June 15, 2026
$6,411
Jun 1 - Aug 31
Due: September 15, 2026
$6,411
Sep 1 - Dec 31
Due: January 15, 2027
$6,411
Don't miss your quarterly payments!
The IRS may charge penalties and interest if you underpay or pay late. Consider setting up automatic payments or calendar reminders.
Colorado Quarterly Tax Highlights
Colorado has a flat 4.4% income tax rate
Simple flat rate makes calculation easy
Use Form 104EP for quarterly payments
State tax is 4.4% of federal taxable income with modifications
Colorado Quarterly Tax FAQ
What is Colorado's income tax rate?
Colorado has a flat 4.4% income tax rate. This applies to all income levels equally, making tax calculation straightforward for self-employed individuals.
How do I pay quarterly taxes in Colorado?
Use Colorado Form 104EP to make quarterly estimated tax payments. Payments are due April 15, June 15, September 15, and January 15.
Colorado Estimated Quarterly Tax Payments for Self-Employed Workers in 2026
Self-employed workers in Colorado face two tax obligations: federal estimated taxes filed with the IRS and state estimated taxes filed with the Colorado Department of Revenue. Colorado imposes a flat 4.4% income tax rate on all taxable income. If you expect to owe $1,000 or more in Colorado state income tax after withholding and credits, you must make quarterly estimated payments using Form 104EP.
Colorado's income tax is calculated as a percentage of your federal taxable income with certain modifications. This means your federal standard deduction and many federal deductions automatically reduce your Colorado tax base.
| Tax Layer | Rate / Range | Filed With | Form |
|---|---|---|---|
| Federal income tax | 10% – 37% | IRS | 1040-ES |
| Self-employment tax | 15.3% | IRS | 1040-ES / SE |
| Colorado state income tax | 4.4% | Colorado Department of Revenue | Form 104EP |
How Colorado's Flat 4.4% Income Tax Affects Your Quarterly Payments
Colorado uses a flat tax rate of 4.4%, which simplifies quarterly tax calculations. Regardless of income level, every dollar of taxable income is taxed at the same rate. This makes it straightforward to estimate your state quarterly payments — simply multiply your projected net self-employment income by 4.4% and divide by four.
For a single self-employed worker in Colorado earning $100,000 in net self-employment income, the estimated annual tax breakdown is:
| Tax Component | Estimated Amount | Calculation Basis |
|---|---|---|
| Federal income tax | ~$11,600 | After $15,700 standard deduction, 2026 brackets |
| Self-employment tax | ~$14,130 | 15.3% on 92.35% of net earnings |
| Colorado state income tax | ~$4,400 | 4.4% flat rate |
| Total annual tax | ~$30,130 | |
| Quarterly payment | ~$7,533 | Total / 4 quarters |
State payments can be made online through the Colorado Department of Revenue portal at tax.colorado.gov, by mail with a Form 104EP voucher, or via electronic funds transfer where available.
Federal Self-Employment Tax and Quarterly Due Dates
All self-employed workers must pay federal self-employment (SE) tax of 15.3% on 92.35% of net earnings. This consists of 12.4% for Social Security (on earnings up to $184,500 in 2026) and 2.9% for Medicare (no cap). An additional 0.9% Medicare surtax applies to earnings above $200,000 (single filers).
Both Colorado and federal estimated tax payments follow the same quarterly schedule:
| Quarter | Income Period | Due Date |
|---|---|---|
| Q1 | January 1 – March 31 | April 15, 2026 |
| Q2 | April 1 – May 31 | June 15, 2026 |
| Q3 | June 1 – August 31 | September 15, 2026 |
| Q4 | September 1 – December 31 | January 15, 2027 |
To avoid underpayment penalties, pay at least 100% of your prior-year tax liability (or 110% if your AGI exceeds $150,000) spread across four equal payments, or at least 90% of your current-year tax. You can deduct 50% of your self-employment tax from your adjusted gross income, reducing both your federal and Colorado taxable income.
Related Calculators
Official References
This calculator uses current federal and Colorado tax rates and schedules:
- IRS Estimated Tax Guidelines
Federal quarterly tax requirements and Form 1040-ES
- Colorado Department of Revenue
Official Colorado tax authority
- IRS Self-Employment Tax
Social Security and Medicare tax information
This calculator provides estimates based on 2026 tax rates. Your actual tax liability may vary based on deductions, credits, and other factors. Consult a tax professional for personalized advice.