Asked about Colorado individual income tax for self-employed individuals or sole proprietors — filing Form DR 0104, CO estimated tax (Form DR 0104EP), Colorado flat tax rate, Colorado additions and subtractions, or any query involving Colorado state income tax compliance.
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General reference only
This Guide is general tax/accounting reference material for AI-assisted workflows. It has not been reviewed for your personal facts, documents, elections, deadlines, residency, filing status, or local procedures. Do not rely on it to file, pay, amend, or take a tax position without review by a qualified professional in the relevant jurisdiction.
Source-cited draft. This Guide is source-cited but has not been reviewed by a licensed practitioner. It may be incomplete, outdated, or wrong.
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Colorado flat income tax rate (TY 2025)
4.4%C.R.S. §39-22; Colorado Department of Revenue — Book 104 (2025 Filing Guide)
Colorado flat income tax rate (TY 2024, prior year)
4.55%C.R.S. §39-22; Colorado Department of Revenue — Book 104 (2025 Filing Guide)
Colorado tax formula
Colorado taxable income × 4.4% = Colorado taxC.R.S. §39-22; Colorado Form DR 0104 Line 13
Colorado starting point for taxable income
Federal taxable income (federal Form 1040, Line 15)C.R.S. §39-22; Colorado Form DR 0104 Line 1
Colorado individual income tax return filing deadline
April 15 (follows federal deadline)C.R.S. §39-22; Colorado Department of Revenue — Book 104 (2025 Filing Guide)
Standard deduction — Single (TY 2025)
$15,000IRC §63 (federal standard deduction, incorporated by Colorado via C.R.S. §39-22)
Standard deduction — Married Filing Jointly (TY 2025)
$30,000IRC §63 (federal standard deduction, incorporated by Colorado via C.R.S. §39-22)
Standard deduction — Married Filing Separately (TY 2025)
$15,000IRC §63 (federal standard deduction, incorporated by Colorado via C.R.S. §39-22)
Standard deduction — Head of Household (TY 2025)
$22,500IRC §63 (federal standard deduction, incorporated by Colorado via C.R.S. §39-22)
Estimated tax payment threshold — net tax owed
> $1,000 in net tax after withholding and creditsC.R.S. §39-22-601; Colorado Form DR 0104EP
Safe harbor — current year percentage
70% of current year taxC.R.S. §39-22-601; Colorado Department of Revenue — Estimated Payments
Safe harbor — prior year percentage (standard)
100% of prior year taxC.R.S. §39-22-601; Colorado Department of Revenue — Estimated Payments
Safe harbor — prior year percentage (high-income)
110% of prior year taxC.R.S. §39-22-601; Colorado Department of Revenue — Estimated Payments
Safe harbor — basis (lesser of)
Lesser of 70% of current year tax or 100% of prior year tax (110% for high-income)C.R.S. §39-22-601; Colorado Department of Revenue — Estimated Payments
Estimated tax payment — Q1 due date
April 15C.R.S. §39-22-601; Colorado Form DR 0104EP
Estimated tax payment — Q2 due date
June 15C.R.S. §39-22-601; Colorado Form DR 0104EP
Estimated tax payment — Q3 due date
September 15C.R.S. §39-22-601; Colorado Form DR 0104EP
Estimated tax payment — Q4 due date
January 15C.R.S. §39-22-601; Colorado Form DR 0104EP
Social Security subtraction — age 55–64
Partial subtraction availableC.R.S. §39-22-104(4); Colorado Form DR 0104AD
Social Security subtraction — age 65+
Full subtraction of Social Security benefits included in federal taxable incomeC.R.S. §39-22-104(4); Colorado Form DR 0104AD
Colorado Form DR 0104 — Federal taxable income line
Line 1Colorado Form DR 0104
Colorado Form DR 0104 — Colorado additions line
Line 3 (from DR 0104AD)Colorado Form DR 0104; Colorado Form DR 0104AD
Colorado Form DR 0104 — Colorado subtractions line
Line 5 (from DR 0104AD)Colorado Form DR 0104; Colorado Form DR 0104AD
Colorado Form DR 0104 — Colorado taxable income line
Line 12Colorado Form DR 0104
Colorado Form DR 0104 — Colorado tax line
Line 13 (4.4% × Line 12)Colorado Form DR 0104
Colorado Form DR 0104 — Alternative minimum tax line
Line 14Colorado Form DR 0104
Colorado Form DR 0104 — Credits line
Line 18 (DR 0104CR)Colorado Form DR 0104; Colorado Form DR 0104CR
Colorado Form DR 0104 — Net tax line
Line 20Colorado Form DR 0104
Colorado Form DR 0104 — Estimated payments line
Line 30Colorado Form DR 0104
Colorado Form DR 0104 — Balance due / refund lines
Lines 36–37Colorado Form DR 0104
Scope. This skill covers Colorado individual income tax for self-employed individuals and sole proprietors filing Form DR 0104. It addresses tax computation, deductions, estimated payments, and form mapping. Quality tier. Q3 — AI-drafted with citations; not independently verified by a licensed professional.
Metadata table
| Field | Value |
|---|---|
| Jurisdiction | Colorado, United States |
| Jurisdiction code | US-CO |
| Tax authority | Colorado Department of Revenue |
| Filing portal | https://revenueonline.colorado.gov |
| Legislation citation | C.R.S. §39-22 (Income Tax) |
| Primary form | DR 0104 — Colorado Individual Income Tax Return |
| Filing deadline | April 15 (follows federal deadline) |
| Version | 0.1 |
| Generated | 2026-05-22 |
| Validation status | AI-drafted — Q3 |
Tax rate table (TY 2025)
| Filing status | Rate | Applies to |
|---|---|---|
| All statuses | 4.4% | All Colorado taxable income |
Colorado imposes a flat income tax rate of 4.4% on all Colorado taxable income, regardless of filing status or income level. The rate was reduced from 4.55% (TY 2024) to 4.4% (TY 2025) through TABOR-related adjustments.
Standard deduction table (TY 2025)
| Filing status | Standard deduction |
|---|---|
| Single | $15,000 |
| Married Filing Jointly | $30,000 |
| Married Filing Separately | $15,000 |
| Head of Household | $22,500 |
Colorado uses the federal standard deduction amounts. For TY 2025: (These are the federal amounts; Colorado taxable income starts from federal taxable income, which already incorporates the federal standard deduction or itemized deductions.)
Colorado's Taxpayer's Bill of Rights (TABOR) limits state revenue growth. When revenue exceeds limits, taxpayers receive refunds. These refunds are typically claimed on the DR 0104 or issued automatically.
Key implication: Because Colorado starts from federal taxable income, the federal standard deduction (or itemized deductions) is already incorporated. Taxpayers cannot separately choose between standard/itemized for Colorado — they must use whatever they chose federally.
Tier 1 rules table
| # | Rule | Logic |
|---|---|---|
| T1-01 | Apply 4.4% flat rate to Colorado taxable income | Single rate × taxable income |
| T1-02 | Start from federal taxable income | Federal Form 1040, Line 15 |
| T1-03 | Social Security subtraction (age 55–64) | Partial subtraction available |
| T1-04 | Social Security subtraction (age 65+) | Full subtraction of benefits included in federal taxable income |
| T1-05 | Estimated tax threshold | Net tax after withholding/credits > $1,000 |
| T1-06 | U.S. government interest subtraction | Subtract interest on U.S. obligations included in federal taxable income |
| T1-07 | State refund addition | Add back state tax refund if itemized in prior year |
Tier 2 rules table
| # | Rule | Why judgment needed |
|---|---|---|
| T2-01 | Colorado-source capital gains subtraction | Must meet holding period and Colorado-source requirements |
| T2-02 | Part-year resident apportionment | Requires Form DR 0104PN and income allocation |
| T2-03 | TABOR refund election | Taxpayer may choose between cash refund or credit against future tax |
| T2-04 | Charitable contribution subtraction | Colorado allows additional subtraction for certain charitable giving (above federal benefit) |
| T2-05 | Multistate income apportionment | Business income from multiple states requires analysis |
| T2-06 | Net operating loss | Colorado follows federal NOL rules with some modifications |
Supplier pattern library table
| Pattern on bank/CC statement | Likely meaning |
|---|---|
CO DEPT OF REVENUE / COLORADO DOR | Colorado income tax payment |
REVENUE ONLINE CO | Payment via Revenue Online portal |
STATE OF CO TAX | State tax payment |
COLORADO DEPT REV | Department of Revenue payment |
CO DR 0104EP | Estimated tax payment |
CO DEPT OF REVENUE / COLORADO DOR — Colorado income tax paymentREVENUE ONLINE CO — Payment via Revenue Online portalSTATE OF CO TAX — State tax paymentCOLORADO DEPT REV — Department of Revenue paymentCO DR 0104EP — Estimated tax paymentForm mapping table
| Computed value | Form DR 0104 line |
|---|---|
| Federal taxable income | Line 1 |
| Colorado additions | Line 3 (from DR 0104AD) |
| Colorado subtractions | Line 5 (from DR 0104AD) |
| Colorado taxable income | Line 12 |
| Colorado tax (4.4% × Line 12) | Line 13 |
| Alternative minimum tax | Line 14 |
| Credits (DR 0104CR) | Line 18 |
| Net tax | Line 20 |
| Estimated payments | Line 30 |
| Balance due / refund | Lines 36–37 |
This skill must refuse and recommend professional review when:
Refusal catalogue table
| # | Condition |
|---|---|
| R-01 | Taxpayer has multistate business activity requiring apportionment |
| R-02 | Taxpayer is a part-year resident with complex sourcing (DR 0104PN) |
| R-03 | Taxpayer has Colorado NOL carryforward with state-specific modifications |
| R-04 | Questions about Colorado enterprise zone credits |
| R-05 | Issues involving Colorado alternative minimum tax |
| R-06 | TABOR refund mechanism questions requiring legal interpretation |
| R-07 | Colorado child care / earned income tax credit calculations |
| R-08 | Audit representation or controversy matters |
| R-09 | Any question about tax fraud, evasion, or aggressive positions |
This skill and its outputs are provided for informational and computational purposes only and do not constitute tax, legal, or financial advice. Open Accountants and its contributors accept no liability for any errors, omissions, or outcomes arising from the use of this skill. All outputs must be reviewed and signed off by a qualified professional (such as a CPA, EA, tax attorney, or equivalent licensed practitioner in your jurisdiction) before filing or acting upon.
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Other Colorado computations in the OpenAccountants Tax Library.
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