State tax docs / States / Colorado

Colorado state income tax: engine rules, 2026

How the QuantCalc engine computes Colorado tax for tax year 2026, rule by rule, with the official source for each rule. Verification status: Worksheet-tested (what this means).

On this page: How the tax is computed · Rate schedule · Deductions, exemptions and credits · Age 65+ subtractions and credits · Social Security · IRA, 401(k) and private pensions · Public pensions · Military retirement pay · Roth conversions · Capital gains · Interaction with the federal return · Blindness and disability · Part-year and nonresident returns · Worked examples · After 2026 · Not calculated · Verification. Machine-readable: this state's entry in the engine config and the provenance file (key CO).

How the tax is computed

Every step the engine takes for Colorado, in the order it takes them. Steps marked with a filing status or household type apply only there. Each step links the section below that carries Colorado's figures and the official sources for it; the calculation order page describes every step for all jurisdictions.

What each filing status gets, read back from the engine for a household with $1 of income (so below every phase-out and income test):

	Single	Married filing jointly	Married filing separately	Head of household
Rate schedule used	single schedule	joint schedule	joint schedule, thresholds halved	single schedule
Top rate	4.4% flat	4.4% flat	4.4% flat	4.4% flat
Standard deduction, under 65	$16,100	$32,200	$16,100	$24,150
Standard deduction at 70 (joint: both 70)	$18,150	$35,500	$17,750	$26,200
Personal exemption	none	none	none	none
Age subtractions at 70 (joint: both 70)	$6,000	$12,000	none	$6,000

Per-person mode joint returns with the spouse's age given On a joint return with the spouse's age given, every age test the state applies per taxpayer is evaluated for each spouse at their own age. Without it one household age applies to both.
engine step (compute_state_tax_detail). Engine convention, no external source: The engine cannot know the second spouse's age unless told.
Blindness and disability, per person only when the caller says a person is blind or disabled The filer is person one; the spouse counts only on a joint return and only when the caller says so (there is no household convention as for age). Where a state lets a disabled person (and, where it says so, a blind one, or one whose spouse is disabled) qualify for its general retirement exclusion before the age, that person is treated as having reached the age for that exclusion only. Of the 42 taxing jurisdictions, these have a blind amount: Arizona, Arkansas, California, Colorado, Delaware, the District of Columbia, Hawaii, Idaho, Illinois, Indiana, Iowa, Kansas, Kentucky, Maine, Maryland, Massachusetts, Michigan, Minnesota, Mississippi, Missouri, Montana, Nebraska, New Jersey, New Mexico, North Dakota, Oklahoma, Oregon, Utah, Vermont and Virginia; these have none: Alabama, Connecticut, Georgia, Louisiana, New York, North Carolina, Ohio, Pennsylvania, Rhode Island, South Carolina, West Virginia and Wisconsin. A disability route is calculated in Arkansas, the District of Columbia, Georgia, Hawaii, Idaho, Iowa, Maryland, Michigan, New Jersey, Oregon and West Virginia.
engine step (compute_state_tax_detail). Engine convention, no external source: Who is blind or disabled is the caller's statement; the engine has no household convention for it.
Rate schedule and standard deduction by filing status Single uses the single schedule and deduction; married filing jointly the joint ones. Head of household and married filing separately follow the two steps below.
Colorado's values · engine step (select_brackets). Sources (Rate schedule): DR 1098 2026 Colorado Withholding Worksheet for Employers (checked 2026-10-12); Book 104 2025 Colorado Individual Income Tax Filing Guide (checked 2026-10-12)
Married filing separately Where the state publishes its own separate schedule, that one (with half the joint deduction unless a separate deduction is set). Where one schedule applies to every status, that schedule unscaled with the single deduction. Otherwise the joint schedule with every threshold and the deduction halved (computed as the joint tax on twice the income, halved).
Colorado's values · engine step (select_brackets). Sources (Rate schedule): DR 1098 2026 Colorado Withholding Worksheet for Employers (checked 2026-10-12); Book 104 2025 Colorado Individual Income Tax Filing Guide (checked 2026-10-12)
Head of household The state's head-of-household schedule where it has one, else the single schedule; the head-of-household deduction where set, else the single deduction.
Colorado's values · engine step (select_brackets). Sources (Rate schedule): DR 1098 2026 Colorado Withholding Worksheet for Employers (checked 2026-10-12); Book 104 2025 Colorado Individual Income Tax Filing Guide (checked 2026-10-12)
The income total every income test uses Other ordinary income + retirement distributions (before any exclusion) + conversion + federally taxable Social Security + long-term gains + Railroad Retirement Tier 2. It stands in for federal adjusted gross income in every threshold, cliff and phase-out below; state subtractions do not reduce it.
engine step (compute_state_tax_detail). Engine convention, no external source: The inputs are the federal AGI components, so their sum is federal AGI for these income types.
Attributing income to each spouse joint returns with each spouse's own amounts given With a caller's split (the API's spouse object), each spouse's own distributions (employer-plan money included), pension, public pension, conversion, wages and military pay; spouse 2's shares are clamped into the household totals and spouse 1 gets the rest. Without a split, in per-person mode, every item is divided 50/50. Social Security is divided by each spouse's own gross benefits where the caller gives spouse.socialSecurityGross, else 50/50; other ordinary income and gains are always divided 50/50 where a rule needs a per-person amount. The split is used only where a state's rule is per taxpayer; household totals stay authoritative for the base and the income tests.
engine step (compute_state_tax_detail). Engine convention, no external source: Equal attribution is the neutral split when the owner of a dollar is not known.
Early IRA distributions The IRA and employer-plan dollars each person took before 59½: the amount the caller gave, else every such dollar of a person under 59 at the end of the year (none of an older person, or when the age is not given). Where the state keeps its retirement break only for some federal early-withdrawal exceptions, the other early dollars leave the retirement pool and are taxed as ordinary income; the exception is the caller's, else death for a survivor's benefits, disability for a disabled person, else none. Where the state taxes only the part over the IRA basis, the part within it is left out altogether. A kept exception passes the state's IRA age gate. The additional state tax on the early dollars with no exception is added before the credits, or after them where the state says so (next steps).
Colorado's values · engine step (compute_state_tax_detail). Sources (IRA, 401(k) and private pensions): Income Tax Topics: Social Security, Pensions, and Annuities (Revised January 2025) (checked 2026-10-12); Individual Income Tax | Information for Retirees (checked 2026-10-12)
Keeping the per-spouse shares inside the household joint returns with each spouse's own amounts given After the public-pension and employer-pension carve-outs, if the two spouses' remaining shares add up to more than the household's exclusion-eligible distributions (an inconsistent split), spouse 1's share is reduced so they do not.
engine step (compute_state_tax_detail). Engine convention, no external source: Input normalisation.
Military retirement pay The state's military rule runs first, on military pay alone, per taxpayer: each spouse's own pay at their own age when attributed, otherwise half each at the household age on a joint return. Exempt dollars leave the base; the rest become pension dollars for the general retirement rules. Where the state lets a disabled retiree qualify at any age, a disabled person is treated as having reached the rule's age.
Colorado's values · engine step (compute_state_tax_detail). Sources (Military retirement pay): Retired servicemembers (checked 2026-10-12); HB26 1062 (checked 2026-10-12)
One taxpayer's military exemption Exempt: all of it (below the age split, up to the younger cap). Capped: up to the cap for the age tier, plus the earned-income bonus below the age split when the taxpayer's own wages exceed the threshold, less the taxpayer's own Social Security where the rule says so. Percentage: the percentage (below the age split, up to the younger cap). Then the income limit: above it the exemption is lost, or phased out over the range where one is set.
Colorado's values · engine step (military_exempt_one). Sources (Military retirement pay): Retired servicemembers (checked 2026-10-12); HB26 1062 (checked 2026-10-12)
Capital-loss deduction off the base The deduction comes off the other ordinary income (negative income, as Form 1040 line 7a is), so the base and every state-AGI figure summed from it carry it; WI no more than Wisconsin ordinary income (Schedule WD line 28(c)). States whose base is federal taxable income (with the caller's figure) already have it there and take it only once. Engine 1.13.1: the allowed rental loss comes off the same way, on its own line (rental_loss_deduction).
Colorado's values · engine step (compute_state_tax_detail). Sources (Capital gains): Book 104 2025 Colorado Individual Income Tax Filing Guide (checked 2026-10-12); 2025 Schedule D (Form 1040), Capital Gains and Losses (checked 2026-10-12)
Colorado: per spouse, own ages joint returns with the spouse's age given Per spouse at their own ages (both ages known): each spouse's own distributions and own Social Security (by the spouse's stated gross benefits, else half) through the subtraction below, at that spouse's age; the income test for ages 55 to 64 uses the joint income total. A conversion is taxed in full, except where the state counts it as a taxable IRA distribution: then it draws what is left of the same subtraction after the distributions.
Colorado's values · engine step (compute_state_tax_detail). Sources (IRA, 401(k) and private pensions): Income Tax Topics: Social Security, Pensions, and Annuities (Revised January 2025) (checked 2026-10-12); Individual Income Tax | Information for Retirees (checked 2026-10-12)
Colorado: per spouse, household age joint returns Joint return without the spouse's age: still per spouse, each at the household age, with the distributions split by the caller's split or 50/50 and Social Security by the spouse's stated gross benefits, else 50/50. A conversion is taxed in full, except where the state counts it as a taxable IRA distribution: then it draws what is left of the same subtraction after the distributions.
Colorado's values · engine step (compute_state_tax_detail). Sources (IRA, 401(k) and private pensions): Income Tax Topics: Social Security, Pensions, and Annuities (Revised January 2025) (checked 2026-10-12); Individual Income Tax | Information for Retirees (checked 2026-10-12)
Colorado: one filer Otherwise (single, separate and head-of-household returns): one subtraction on the whole amount. A conversion is taxed in full, except where the state counts it as a taxable IRA distribution: then it draws what is left of the same subtraction after the distributions.
Colorado's values · engine step (compute_state_tax_detail). Sources (IRA, 401(k) and private pensions): Income Tax Topics: Social Security, Pensions, and Annuities (Revised January 2025) (checked 2026-10-12); Individual Income Tax | Information for Retirees (checked 2026-10-12)
Colorado Social Security and pension subtraction 65 or older: Social Security fully subtracted; pension and annuity income up to $24,000 less the Social Security subtracted. 55 to 64 with income at or below the threshold: the same with a $20,000 cap. 55 to 64 above it: one shared $20,000, Social Security first. Under 55: no subtraction, except a survivor's death benefit (its own step).
Colorado's values · engine step (co_retirement_in_state_base). Sources (IRA, 401(k) and private pensions): Income Tax Topics: Social Security, Pensions, and Annuities (Revised January 2025) (checked 2026-10-12); Individual Income Tax | Information for Retirees (checked 2026-10-12)
Which Social Security threshold applies Joint returns use the joint threshold; head of household uses it too where the state says so, otherwise the single one; married filing separately uses its own threshold where set, else the single one. Benefits are tested against the income total above.
Colorado's values · engine step (ss_amount_in_state_base). Sources (Social Security): Income Tax Topics: Social Security, Pensions, and Annuities (Revised January 2025) (checked 2026-10-12); HB24-1142 Social Security Income Tax Subtraction (checked 2026-10-12); SB25-136 (2025 Regular Session) bill page (checked 2026-10-12); HB24-1142 (signed act; Internet Archive capture) (checked 2026-09-28)
Social Security: Colorado age bands (Social Security alone) The same age bands as the Colorado subtraction, on Social Security alone. In a calculation Colorado always takes the joint subtraction above; this branch serves callers of the Social Security rule by itself.
Colorado's values · engine step (ss_amount_in_state_base). Sources (Social Security): Income Tax Topics: Social Security, Pensions, and Annuities (Revised January 2025) (checked 2026-10-12); HB24-1142 Social Security Income Tax Subtraction (checked 2026-10-12); SB25-136 (2025 Regular Session) bill page (checked 2026-10-12); HB24-1142 (signed act; Internet Archive capture) (checked 2026-09-28)
Long-term gains in the base Where gains are taxed as ordinary income: net long-term gain less the flat exclusion (never below zero), times the inclusion share. Elsewhere none enters.
Colorado's values · engine step (compute_state_tax_detail). Sources (Capital gains): Book 104 2025 Colorado Individual Income Tax Filing Guide (checked 2026-10-12); 2025 Schedule D (Form 1040), Capital Gains and Losses (checked 2026-10-12)
Additional standard deduction at 65 The unmarried amount for a single or head-of-household filer 65 or older, the married amount for each spouse 65 or older, added to the standard deduction before any phase-out.
Colorado's values · engine step (compute_state_tax_detail). Sources (Deductions, exemptions and credits): IRS releases tax inflation adjustments for tax year 2026, including amendments from the One, Big, Beautiful Bill (checked 2026-10-12); Book 104 2025 Colorado Individual Income Tax Filing Guide (checked 2026-10-12); Individual Income Tax Guide (checked 2026-10-12); IRS releases tax inflation adjustments for tax year 2026 (checked 2026-10-12); 26 U.S.C. § 151 (checked 2026-10-12); Child Tax Credit & Earned Income Tax Credit (web page) (checked 2026-10-12); 2025 DR 0104TN Colorado EITC for ITIN Filers or Certain Filers Under Age 25 (checked 2026-10-12)
Additional standard deduction for blindness only when the caller says a person is blind or disabled The unmarried amount for a blind single or head-of-household filer, the married amount for each blind spouse, added to the standard deduction before any phase-out. Age and blindness are separate boxes, so a person 65 or older and blind gets both.
Colorado's values · engine step (compute_state_tax_detail). Sources (Blindness and disability): Rev. Proc. 2025-32 (2026 inflation adjustments) (checked 2026-10-12)
Standard deduction limited at high income Above the income threshold the deduction (with its age and blindness amounts) is limited to the status amount: the state adds the rest back. On the component path only; where the caller supplies federal taxable income that figure is used as given.
Colorado's values · engine step (compute_state_tax_detail). Sources (Deductions, exemptions and credits): IRS releases tax inflation adjustments for tax year 2026, including amendments from the One, Big, Beautiful Bill (checked 2026-10-12); Book 104 2025 Colorado Individual Income Tax Filing Guide (checked 2026-10-12); Individual Income Tax Guide (checked 2026-10-12); IRS releases tax inflation adjustments for tax year 2026 (checked 2026-10-12); 26 U.S.C. § 151 (checked 2026-10-12); Child Tax Credit & Earned Income Tax Credit (web page) (checked 2026-10-12); 2025 DR 0104TN Colorado EITC for ITIN Filers or Certain Filers Under Age 25 (checked 2026-10-12)
Federal senior deduction taken against the state base For each taxpayer 65 or older: the amount, reduced by the rate times the income total above the status's start (joint start on a joint return); none for married filing separately. In the states whose base is federal taxable income it is taken only when the caller does not supply that figure (it is already in it).
Colorado's values · engine step (compute_state_tax_detail). Sources (Age 65+ subtractions and credits): Rev. Proc. 2025-32 (2026 inflation adjustments) (checked 2026-10-12); Schedule 1-A (Form 1040), Additional Deductions (checked 2026-10-12); 2025 Colorado Individual Income Tax Filing Guide (checked 2026-10-12)
Survivor benefits below the age only when the caller gives the person facts (a civil service annuity, disability pay, Social Security disability, survivor benefits, an IRA basis or an exception) Below the pension subtraction's age, a person whose pension and IRA income is received as a beneficiary subtracts it up to the cap. Where the state says so, the person's own taxable Social Security received as survivor benefits shares the same cap.
Colorado's values · engine step (compute_state_tax_detail). Sources (IRA, 401(k) and private pensions): Income Tax Topics: Social Security, Pensions, and Annuities (Revised January 2025) (checked 2026-10-12); Individual Income Tax | Information for Retirees (checked 2026-10-12)
State taxable income Other ordinary income + Social Security, retirement income, conversion and gains left in the base − standard deduction − personal exemption − age subtractions.
engine step (compute_state_tax_detail). Engine convention, no external source: The order of subtraction follows the state forms; each amount is sourced at its own step.
Starting from federal taxable income only when the caller supplies federal taxable income (the planner; not the API) When the caller supplies federal taxable income (the planner does; the API does not), the base starts from it, adds the gains in it (less the state's gain subtraction), and subtracts the state's own exclusions and subtractions; the state's deduction is not subtracted again.
Colorado's values · engine step (compute_state_tax_detail). Sources (Interaction with the federal return): Book 104 2025 Colorado Individual Income Tax Filing Guide (checked 2026-10-12)
No tax at or below zero State taxable income at or below zero returns a tax of 0 (credits are not refundable), unless the state has a tax computed apart from taxable income that still applies (next step).
engine step (compute_state_tax_detail). Engine convention, no external source: Every credit the engine carries is nonrefundable, so nothing below can make a zero tax negative; each credit is sourced at its own step.
Separate-return scaling married filing separately For the halved-joint rule, taxable income is doubled before the schedule and the result halved.
Colorado's values · engine step (compute_state_tax_detail). Sources (Rate schedule): DR 1098 2026 Colorado Withholding Worksheet for Employers (checked 2026-10-12); Book 104 2025 Colorado Individual Income Tax Filing Guide (checked 2026-10-12)
The rate schedule Each bracket's rate on the part of taxable income inside it, summed. No rounding: the result is carried in full precision.
Colorado's values · engine step (apply_state_brackets). Sources (Rate schedule): DR 1098 2026 Colorado Withholding Worksheet for Employers (checked 2026-10-12); Book 104 2025 Colorado Individual Income Tax Filing Guide (checked 2026-10-12)
Credits cannot make the tax negative The credits are subtracted and the result floored at zero.
engine step (compute_state_tax_detail). Engine convention, no external source: Every credit the engine carries is nonrefundable; each credit is sourced at its own step.
Qualifying surviving spouse qualifying surviving spouse returns A qualifying surviving spouse (filingStatus qss) is one person on the return, taxed from the single figures with the state's own treatment of the status laid over them: where the state says so, the joint rate schedule, the joint standard deduction, the joint personal exemption, the joint income limits and phase-outs (only those the state sets for joint returns), the married 65+ and blindness amounts, or the head-of-household return; where the state gives the status nothing of its own, the single return. The federal figures the engine derives for the status are the federal qualifying-surviving-spouse ones (the joint standard deduction, the married 65+ amount).
Colorado's values · engine step (state_tax_effective_config). Sources (Rate schedule): DR 1098 2026 Colorado Withholding Worksheet for Employers (checked 2026-10-12); Book 104 2025 Colorado Individual Income Tax Filing Guide (checked 2026-10-12)
Railroad Retirement benefits only when the caller gives Railroad Retirement benefits Railroad Retirement benefits are never taxed by a state (45 U.S.C. §231m). Tier 2 (railroadRetirementTier2) is in the income total the tests use but never in the base. Tier 1 (railroadRetirementTier1) is a part of the gross benefits (socialSecurityGross); its share of the taxable benefits is taken out of the Social Security every state rule sees, so a state that taxes Social Security never reaches it. Where a state's worksheet says so, the benefits reduce a retirement cap or subtraction (ID, IN, MD, ME, MN: both tiers; MI: the taxable railroad benefits); Minnesota's and Utah's Social Security rules test an income without them, Minnesota's, New Jersey's and California's retirement income tests an income without Tier 2; Ohio and Delaware test their own AGI everywhere, which never holds the benefits.
Colorado's values · engine step (compute_state_tax_detail). Sources (Social Security): Income Tax Topics: Social Security, Pensions, and Annuities (Revised January 2025) (checked 2026-10-12); HB24-1142 Social Security Income Tax Subtraction (checked 2026-10-12); SB25-136 (2025 Regular Session) bill page (checked 2026-10-12); HB24-1142 (signed act; Internet Archive capture) (checked 2026-09-28)
The capital-loss deduction the state allows With a net capital loss (capitalLoss): the smaller of the loss and the state's limit (the federal $3,000 / $1,500 where the state follows the federal return; MA $2,000, and no more than the interest and dividends); AL the loss less the part carried in, unlimited; PA and NJ none. It comes off the income total the income tests use (and the Social Security worksheets' income); the gross-income filing test (LA) reads the total before it. Engine 1.13.1: with a rental loss (rentalNetIncome below 0, the federal Schedule E line 26 amount) the state allows, the whole loss where the state starts from federal AGI or follows the federal schedule, none in PA and NJ (rental_loss_no_offset): it comes off the same income the same way; a rental profit is other ordinary income.
Colorado's values · engine step (compute_state_tax_detail). Sources (Capital gains): Book 104 2025 Colorado Individual Income Tax Filing Guide (checked 2026-10-12); 2025 Schedule D (Form 1040), Capital Gains and Losses (checked 2026-10-12)
Each spouse's own Social Security joint returns On a joint return, each spouse's own Social Security is the spouse's share of the benefits by spouse.socialSecurityGross when the caller gives it (Tier 1 railroad benefits left out), else half each. It is what the per-spouse rules read: Colorado's per-spouse subtraction, Rhode Island's per-spouse modification, and the Maine, Maryland and other retirement caps reduced by the benefits each spouse received (with each spouse's own railroad benefits where the state counts them).
Colorado's values · engine step (compute_state_tax_detail). Sources (Social Security): Income Tax Topics: Social Security, Pensions, and Annuities (Revised January 2025) (checked 2026-10-12); HB24-1142 Social Security Income Tax Subtraction (checked 2026-10-12); SB25-136 (2025 Regular Session) bill page (checked 2026-10-12); HB24-1142 (signed act; Internet Archive capture) (checked 2026-09-28)
Refundable state credits The credits paid beyond the tax (reported in refundableCredits; netTax = totalTax less them): earned income credits as a share of the federal EIC with each state's own age band (OK on the 2020 federal credit, DC's own childless schedule, the CalEITC table, MN's Working Family Credit), the NYC EIC and school tax credits, and the property-tax, renter, grocery and senior credits of MA, MI, NJ, ID, HI, NM, OK, AZ, NY, RI, WV, ME, DC, MN, MO, WI, IN and MT, each on its own income measure. Engine 1.13.1: a part-year NYC resident's school tax credits (the Table 2 proration chart and the rate-reduction amount on IT-360.1 line 47; IT-203 lines 60 / 60a for a part-year state resident).
Colorado's values · engine step (state_tax_refundable_credits). Sources (Deductions, exemptions and credits): IRS releases tax inflation adjustments for tax year 2026, including amendments from the One, Big, Beautiful Bill (checked 2026-10-12); Book 104 2025 Colorado Individual Income Tax Filing Guide (checked 2026-10-12); Individual Income Tax Guide (checked 2026-10-12); IRS releases tax inflation adjustments for tax year 2026 (checked 2026-10-12); 26 U.S.C. § 151 (checked 2026-10-12); Child Tax Credit & Earned Income Tax Credit (web page) (checked 2026-10-12); 2025 DR 0104TN Colorado EITC for ITIN Filers or Certain Filers Under Age 25 (checked 2026-10-12)

Rate schedule

A flat 4.4% on state taxable income.

Source review notes (what the sources do not state outright, or what the engine does not carry):

No TY2026 DR 0104 booklet is published yet; a TABOR-triggered temporary rate reduction for 2026 (as in 2024, 4.25%) would not be visible until the 2026 booklet. The C.R.S. 39-22-104 statute text on leg.colorado.gov returned HTTP 403 to the checker.

DR 1098 2026 Colorado Withholding Worksheet for Employers, Colorado Department of Revenue. Colorado's 2026 wage-withholding computation applies a single flat rate of 4.40% to annualized taxable wages. Checked 2026-10-12.
Book 104 2025 Colorado Individual Income Tax Filing Guide, Colorado Department of Revenue. Colorado income tax is a single flat rate of 4.4% of Colorado taxable income for every filing status (2025 filing guide, latest published). Checked 2026-10-12.

Deductions, exemptions and credits

Standard deduction (or the exemption the engine carries in its place): $16,100 single, $32,200 married filing jointly, $24,150 head of household.
The standard deduction includes $2,050 more for a single or head-of-household filer 65 or older, and $1,650 more for each spouse 65 or older on a married return.
Above $300,000 of income the deduction (with its age and blindness amounts) is limited to $1,000 ($2,000 for a married couple filing jointly); the rest is added back. The engine applies this where it rebuilds the base itself (the API); where federal taxable income is supplied, that figure is used as given.

Source review notes (what the sources do not state outright, or what the engine does not carry):

The engine's federal-coupled deduction is used only on the component-model path; the v4 path uses the caller's actual federal taxable income (state_base_is_federal_taxable_income).

IRS releases tax inflation adjustments for tax year 2026, including amendments from the One, Big, Beautiful Bill, Internal Revenue Service. Colorado has no state standard deduction; because Colorado starts from federal taxable income, the engine's deduction values are the 2026 federal standard deduction of $16,100 single and $32,200 married filing jointly. Checked 2026-10-12.
Book 104 2025 Colorado Individual Income Tax Filing Guide, Colorado Department of Revenue. DR 0104 line 1 is federal taxable income (Form 1040 line 15), so the federal standard or itemized deduction is already taken before Colorado's computation begins. The standard or itemized deduction addback: the $12,000 (2026: $1,000) limit for every federal status but married filing jointly, the $16,000 (2026: $2,000) limit for a joint return; a qualifying surviving spouse does not file a joint return. Earned income credit (engine 1.12.0, refundableCredits): 25% of the federal EIC for 2026. Checked 2026-10-12.
Individual Income Tax Guide, Colorado Department of Revenue. Above $300,000 of federal AGI the federal standard (or itemized) deduction is added back beyond $1,000 ($2,000 joint) for 2026 and later. Checked 2026-10-12.
IRS releases tax inflation adjustments for tax year 2026, Internal Revenue Service. The 2026 federal standard deduction for heads of household, which the state uses. Checked 2026-10-12.
26 U.S.C. § 151, Legal Information Institute (Cornell Law School). The federal senior deduction Colorado's base carries phases out over $75,000 of MAGI, $150,000 only 'in the case of a joint return': a qualifying surviving spouse is on $75,000. Checked 2026-10-12.
Child Tax Credit & Earned Income Tax Credit (web page), Colorado Department of Revenue, Taxation Division. Earned income credit (engine 1.12.0, refundableCredits): 25% of the federal EIC for 2026. Checked 2026-10-12.
2025 DR 0104TN Colorado EITC for ITIN Filers or Certain Filers Under Age 25, Colorado Department of Revenue. Earned income credit (engine 1.12.0, refundableCredits): 25% of the federal EIC for 2026. Checked 2026-10-12.

Age 65+ subtractions and credits

The federal senior deduction is also taken against the state base: $6,000 for each taxpayer 65 or older, each reduced by 6% of income above $75,000 (single and head of household) or $150,000 (MFJ). Married couples filing separately get none. (The state starts from federal taxable income, which already carries it; the engine adds it only where it rebuilds the base itself.)

Rev. Proc. 2025-32 (2026 inflation adjustments), Internal Revenue Service. The federal additional standard deduction for 2026, per condition (age 65 and blindness each count): $2,050 unmarried, $1,650 married. The state takes it where its deduction is the federal one. Checked 2026-10-12.
Schedule 1-A (Form 1040), Additional Deductions, Internal Revenue Service. The federal senior deduction: $6,000 per taxpayer 65 or older, reduced by 6% of modified AGI over $75,000 ($150,000 joint); none for married filing separately. Checked 2026-10-12.
2025 Colorado Individual Income Tax Filing Guide, Colorado Department of Revenue. Colorado starts from federal taxable income (Form 1040 line 15), which carries the federal age and blindness amounts and the senior deduction. Checked 2026-10-12.

Social Security

From age 65, fully subtracted at any income. From 55 to 64, fully subtracted when income is at or below $75,000 (single) and $95,000 (married filing jointly); above it, one $20,000 subtraction is shared with pension and annuity income, Social Security first. Below 55, only benefits received because the person entitled to them died qualify (up to $20,000); Social Security the person receives as survivor benefits (socialSecuritySurvivor: true) is such a death benefit: the engine subtracts the person's taxable benefits within that cap, which pension and IRA survivor income (survivorBenefits) shares. Without that field it subtracts none below that age.

API value: socialSecurityRule: "age_banded_subtraction". The engine's input is the federally taxable amount; income tests use the sum of the income components as the adjusted-gross-income proxy.

Income Tax Topics: Social Security, Pensions, and Annuities (Revised January 2025), Colorado Department of Revenue. Taxable Social Security is fully subtractable at age 65+, fully subtractable at ages 55-64 when AGI is at most $75,000 single / $95,000 joint, and otherwise falls under the $20,000 pension/annuity cap (no subtraction under 55 except death benefits). Social Security is pension and annuity income for the subtraction; under 55 the subtraction is allowed on a death benefit up to $20,000 (survivor Social Security: socialSecuritySurvivor; engine 1.8.0 final). Checked 2026-10-12.
HB24-1142 Social Security Income Tax Subtraction, Colorado General Assembly. HB24-1142 (signed June 6, 2024) extended the full Social Security subtraction to filers aged 55-64 with AGI of at most $75,000 filing individually or $95,000 filing jointly. Checked 2026-10-12.
SB25-136 (2025 Regular Session) bill page, Colorado General Assembly. SB25-136, which would have extended the full subtraction further, was postponed indefinitely in Senate committee on February 27, 2025 and is not law. Checked 2026-10-12.
HB24-1142 (signed act; Internet Archive capture), Colorado General Assembly. C.R.S. 39-22-104(4)(f)(III): the 55-64 full Social Security subtraction below $75,000 of AGI 'if filing individually' and $95,000 'if filing jointly': a qualifying surviving spouse files individually, so the single limit is the statute's. Checked 2026-09-28.

IRA, 401(k) and private pensions

Pension, annuity and IRA/401(k) distributions get a subtraction of up to $24,000 from age 65, and up to $20,000 from age 55. The cap is reduced by the Social Security subtraction claimed; for filers 55-64 over the income threshold the $20,000 is shared with Social Security. Below 55: no subtraction ($0), except a death benefit — pension or IRA income received as a survivor (survivorBenefits) — up to $20,000; a survivor's military retirement pay takes the military subtraction or the death-benefit one, whichever is larger, not both. On a joint return the cap is per spouse, against each spouse's own income, even when only one household age is given.

Source review notes (what the sources do not state outright, or what the engine does not carry):

No Colorado source states the caps for TY2026 specifically; the January 2025 publication and the retirees page are the latest (SB25-136, which would have changed them, died).

Income Tax Topics: Social Security, Pensions, and Annuities (Revised January 2025), Colorado Department of Revenue. Taxpayers 55+ may subtract taxable pension, annuity and certain IRA distributions up to $20,000 (ages 55-64) or $24,000 (65+), reduced by any Social Security subtraction claimed; premature distributions do not qualify. Engine 1.7.0: under 55 the pension and annuity subtraction is allowed only on a death benefit, up to $20,000; federally penalized (premature) distributions never qualify. Checked 2026-10-12.
Individual Income Tax | Information for Retirees, Colorado Department of Revenue. Qualified taxpayers under 65 subtract the smaller of $20,000 or taxable pension/annuity income; those 65+ subtract the smaller of $24,000 or that income. Checked 2026-10-12.
Retired Servicemembers, Colorado Department of Revenue. Engine 1.8.0: a retired servicemember may claim one of two subtractions for military retirement benefits; under 55 a survivor's military pay takes the $15,000 military subtraction or the $20,000 death-benefit one, whichever is larger, not both. Checked 2026-10-12.

Public pensions

No separate treatment: public pensions follow the rules for other retirement income above.

Source review notes (what the sources do not state outright, or what the engine does not carry):

The PERA/DPSRS contribution-basis subtraction is not modeled.

Income Tax Topics: Social Security, Pensions, and Annuities (Revised January 2025), Colorado Department of Revenue. Government pensions (including PERA/DPSRS) share the same $20,000/$24,000 pension and annuity subtraction as private pensions; the separate PERA/DPSRS subtraction covers only 1984-1986 contributions and is not modeled. Checked 2026-10-12.

Military retirement pay

Below age 55, up to $15,000 of military retirement pay is exempt per taxpayer. From age 55 there is no separate military exemption: the pay is pension income under the general retirement rules above.
Military pay the military rule does not exempt is pension income under the general retirement rules.
Rules are applied per taxpayer at that person's own age when the spouse's age is given. API value: rules.militaryRetirement.treatment: "capped_exclusion".

Retired servicemembers, Colorado Department of Revenue. Under 55, a servicemember may subtract up to $15,000 of military retirement pay; at 55 and older it counts toward the general pension and annuity subtraction. Checked 2026-10-12.
HB26 1062, Colorado General Assembly. Under 55, a servicemember may subtract up to $15,000 of military retirement pay; at 55 and older it counts toward the general pension and annuity subtraction. Checked 2026-10-12.

Roth conversions

A conversion is a traditional IRA distribution (Form 1040 line 4b) and never a premature one, so from age 55 it draws the pension and annuity subtraction together with the person's other qualifying retirement income, within the same cap (up to $20,000 from 55, $24,000 from 65); the part above the cap, and a conversion below 55, is taxed as ordinary income.

Source review notes (what the sources do not state outright, or what the engine does not carry):

No official Colorado guidance names Roth conversions; the engine reads the Department's own list of qualifying income (line 4b traditional IRA distributions, premature ones excluded) and lets a conversion at 55+ draw the subtraction (engine 1.8.0, DIFF-CO-01).

Book 104 2025 Colorado Individual Income Tax Filing Guide, Colorado Department of Revenue. Colorado starts from federal taxable income (Form 1040 line 15), so the taxable amount of a Roth conversion enters the Colorado base as ordinary income. Checked 2026-10-12.
Income Tax Topics: Social Security, Pensions, and Annuities (Revised January 2025), Colorado Department of Revenue. Only 'certain' IRA distributions qualify for the pension subtraction: those reported on line 4b, including distributions from a traditional IRA, except premature (penalized) ones. The publication does not name conversions; a conversion is a traditional IRA distribution on line 4b and never premature, so from engine 1.8.0 it draws the subtraction within the cap (DIFF-CO-01). Checked 2026-10-12.

Capital gains

Net long-term gain is taxed as ordinary income.
Short-term gains are ordinary income.

Book 104 2025 Colorado Individual Income Tax Filing Guide, Colorado Department of Revenue. Long-term capital gains are part of federal taxable income and are taxed at the same flat 4.4% rate as other income; the only gain subtraction in the booklet is for Colorado agricultural land (not modeled). Checked 2026-10-12.
2025 Schedule D (Form 1040), Capital Gains and Losses, Internal Revenue Service. The federal return deducts a net capital loss up to $3,000 ($1,500 married filing separately) on Form 1040 line 7a; a state that starts from federal adjusted gross income or federal taxable income carries that deduction. Checked 2026-10-12.

Interaction with the federal return

The state base starts from federal taxable income when the caller supplies it (engine input fed_taxable_ordinary, used by the planner; the API does not take it), so the real federal deductions carry through; otherwise the engine rebuilds the base from income components minus the deduction shown above.

Source review notes (what the sources do not state outright, or what the engine does not carry):

C.R.S. 39-22-104 (statutory definition) could not be fetched (leg.colorado.gov CRS PDF returned 403).

Book 104 2025 Colorado Individual Income Tax Filing Guide, Colorado Department of Revenue. The Colorado computation starts from federal taxable income on Form 1040 line 15 (DR 0104 line 1), which the engine mirrors with state_base_is_federal_taxable_income. Checked 2026-10-12.

Blindness and disability

The standard deduction includes $2,050 more for a blind single or head-of-household filer and $1,650 more for each blind spouse on a married return. Age and blindness are separate: a person 65 or older and blind gets both amounts.
The API applies these through its blind, disabled, spouse.blind and spouse.disabled fields; absent means false.

Rev. Proc. 2025-32 (2026 inflation adjustments), Internal Revenue Service. The federal additional standard deduction for 2026, per condition (age 65 and blindness each count): $2,050 unmarried, $1,650 married. The state takes it where its deduction is the federal one. Checked 2026-10-12.

Part-year and nonresident returns

Part-year resident (DR 0104PN): the tax a full-year resident would owe on all the year's income, times the state's income ratio.
Nonresident (DR 0104PN): the tax a full-year resident would owe on all the year's income, times the state's income ratio.
The ratio: the state's own AGI (after its subtractions) of the state's income over the state AGI of the whole year, rounded to 6 places, which may exceed 1.
A nonresident's retirement income is not taxable by the state (4 U.S.C. §114); the API refuses it in residency.stateIncome. The credit for tax paid to another state and the earned income credits on these returns are not computed.

Married couples whose residency differs (engine 1.13.0)

With residency.spouse on a joint request, each allowed treatment is calculated and reported in residency.couple; tax is the required one, else the state's default, else the couple's residency.election, else the joint return the request's mfj names. Each rule is quoted from the state's instructions (engine 1.14.0: and its statutes, regulations, bulletins and other official guidance) in the sources below.

Spouses	Colorado's rule
One spouse a full-year resident, the other a part-year resident	a joint part-year / nonresident return is required.
One spouse a full-year resident, the other a nonresident	a joint part-year / nonresident return is required.
One spouse a part-year resident, the other a nonresident	a joint part-year / nonresident return is required.
Both part-year residents, different resident periods	a joint part-year / nonresident return is required.
Both nonresidents, only one with income from the state	a joint part-year / nonresident return is required.

DR 0104PN (09/24/25) Form 104PN Part-Year Resident/Nonresident Tax Calculation Schedule 2025, Colorado Department of Revenue. Part-year / nonresident return (engine 1.12.0, residency): Tax computed on full Colorado taxable income (DR 0104 line 12, all-year, as if resident) at the flat rate, multiplied by the apportionment percentage (DR 0104PN line 34 = modified Colorado AGI / modified federal AGI). Checked 2026-10-12.
Income Tax Topics: Part-Year Residents & Nonresidents (Revised February 2024), Colorado Department of Revenue. Part-year / nonresident return (engine 1.12.0, residency): Tax computed on full Colorado taxable income (DR 0104 line 12, all-year, as if resident) at the flat rate, multiplied by the apportionment percentage (DR 0104PN line 34 = modified Colorado AGI / modified federal AGI). Checked 2026-10-12.
Colorado 2025 Individual Income Tax Filing Guide (Book 104), Colorado Department of Revenue. Part-year / nonresident return (engine 1.12.0, residency): Tax computed on full Colorado taxable income (DR 0104 line 12, all-year, as if resident) at the flat rate, multiplied by the apportionment percentage (DR 0104PN line 34 = modified Colorado AGI / modified federal AGI). Checked 2026-10-12.
Income Tax Topics: Part-Year Residents & Nonresidents (Revised February 2024), Colorado Department of Revenue. Married couples whose residency differs (engine 1.13.0): Checked 2026-10-12.

Worked examples

Computed by the engine for the fixed households below (the same ones for every state, so states compare directly). Federal tax is not supplied, so a federal-tax deduction is not taken; the income tests use the sum of the components as income.

Household (engine inputs)	State tax
Single, 67: $30,000 private pension, $20,000 IRA, $10,000 interest, $24,000 Social Security ($17,000 federally taxable), $5,000 long-term gain	$1,507.88
Married filing jointly, 70: $40,000 public pension, $40,000 IRA, $20,000 interest, $40,000 Social Security ($34,000 federally taxable), $10,000 long-term gain	$2,134
Single, 60: $60,000 other ordinary income and a $50,000 Roth conversion	$3,251.60
Married filing jointly, 66: $30,000 IRA, a $40,000 Roth conversion, $30,000 Social Security ($25,500 federally taxable)	$0
Single, 58: $36,000 military retirement pay and $30,000 wages	$1,315.60
Married filing jointly, ages 67 and 61: $50,000 IRA, $10,000 interest, $30,000 Social Security ($25,500 federally taxable), each spouse's age given	$72.60

Line by line

The intermediate lines the engine records while it computes each example (its detail record, printed as it comes out; lines that are zero are left out). The engine's documentation build checks that the lines add up to the taxable income and the tax, for every state, filing status and a grid of households. Each line links the engine step that produces it.

Single, 67: $30,000 private pension, $20,000 IRA, $10,000 interest, $24,000 Social Security ($17,000 federally taxable), $5,000 long-term gain: $1,507.88

Line	Amount
Income total used by the income tests	$82,000
Retirement income and conversions excluded (not in the base)	$7,000
+ Other ordinary income in the base	$10,000
+ Retirement income in the base	$43,000
+ Long-term gain in the base	$5,000
− Standard deduction	$18,150
− Age subtractions and deductions	$5,580
= State taxable income	$34,270
Tax from the rate schedule	$1,507.88
= Tax before credits	$1,507.88
= Tax	$1,507.88

Married filing jointly, 70: $40,000 public pension, $40,000 IRA, $20,000 interest, $40,000 Social Security ($34,000 federally taxable), $10,000 long-term gain: $2,134

Line	Amount
Income total used by the income tests	$144,000
Retirement income and conversions excluded (not in the base)	$14,000
+ Other ordinary income in the base	$20,000
+ Retirement income in the base	$66,000
+ Long-term gain in the base	$10,000
− Standard deduction	$35,500
− Age subtractions and deductions	$12,000
= State taxable income	$48,500
Tax from the rate schedule	$2,134
= Tax before credits	$2,134
= Tax	$2,134

Single, 60: $60,000 other ordinary income and a $50,000 Roth conversion: $3,251.60

Line	Amount
Income total used by the income tests	$110,000
Retirement income and conversions excluded (not in the base)	$20,000
+ Other ordinary income in the base	$60,000
+ Roth conversion in the base	$30,000
− Standard deduction	$16,100
= State taxable income	$73,900
Tax from the rate schedule	$3,251.60
= Tax before credits	$3,251.60
= Tax	$3,251.60

Married filing jointly, 66: $30,000 IRA, a $40,000 Roth conversion, $30,000 Social Security ($25,500 federally taxable): $0

Line	Amount
Income total used by the income tests	$95,500
Retirement income and conversions excluded (not in the base)	$22,500
+ Retirement income in the base	$7,500
+ Roth conversion in the base	$40,000
− Standard deduction	$35,500
− Age subtractions and deductions	$12,000
= State taxable income	$0
Tax from the rate schedule	$0
= Tax	$0

Single, 58: $36,000 military retirement pay and $30,000 wages: $1,315.60

Line	Amount
Income total used by the income tests	$66,000
Retirement income and conversions excluded (not in the base)	$20,000
+ Other ordinary income in the base	$30,000
+ Retirement income in the base	$16,000
− Standard deduction	$16,100
= State taxable income	$29,900
Tax from the rate schedule	$1,315.60
= Tax before credits	$1,315.60
= Tax	$1,315.60

Married filing jointly, ages 67 and 61: $50,000 IRA, $10,000 interest, $30,000 Social Security ($25,500 federally taxable), each spouse's age given: $72.60

Line	Amount
Income total used by the income tests	$85,500
Retirement income and conversions excluded (not in the base)	$18,500
+ Other ordinary income in the base	$10,000
+ Retirement income in the base	$31,500
− Standard deduction	$33,850
− Age subtractions and deductions	$6,000
= State taxable income	$1,650
Tax from the rate schedule	$72.60
= Tax before credits	$72.60
= Tax	$72.60

After 2026: how the amounts move

A request with projection (API) estimates a later tax year from these rules: every dollar amount and age test below moves the way Colorado's law moves it. Rates and the rules themselves stay the 2026 ones (how projection works).

Amounts (engine fields)	After 2026	What the law says, and the source
`std_deduction_single`, `std_deduction_mfj`, `std_deduction_hoh`, `std_deduction_aged_add_unmarried`, `std_deduction_aged_add_married`, `blind_std_add_unmarried`, `blind_std_add_married`	Tied to an indexed federal amount: federal standard deduction under IRC 63(c) and the IRC 63(f) additional amounts for age/blindness, indexed by the IRC 1(f)(3) C-CPI-U cost-of-living adjustment; the increase rounded down to a multiple of $50.	Colorado taxable income starts from federal taxable income, so the deduction is the federal standard deduction with the IRC 63(f) aged/blind additions, indexed federally (increases rounded down to $50). Book 104: 2025 Colorado Individual Income Tax Filing Guide (Colorado Department of Revenue, instructions): Colorado tax starts from federal taxable income (Form 1040 line 15), which carries the federal standard deduction, the 63(f) amounts and the senior deduction. Quoted: "Enter your federal taxable income from your federal income tax form 1040, 1040 SR, or 1040 SP, line 15.". Checked 2026-10-12. 26 U.S.C. 63 (Taxable income defined) (Legal Information Institute (Cornell) - U.S. Code, federal): IRC 63(c)(4) indexes the basic standard deduction and the subsection (f) additional amounts for age and blindness by the IRC 1(f)(3) cost-of-living adjustment. Quoted: "each dollar amount contained in paragraph (2)(B), (2)(C), or (5) or subsection (f) shall be increased by an amount equal to". Checked 2026-10-12. 26 U.S.C. 1 (Tax imposed), subsection (f)(7) (Legal Information Institute (Cornell) - U.S. Code, federal): IRC 1(f)(7)(A): increases under 1(f)(2)(A) (brackets), 63(c)(4) (standard deduction) and 151(d)(4) are rounded down to a multiple of $50. Quoted: "section 63(c)(4), section 68(b)(2) [1] or section 151(d)(4) is not a multiple of $50, such increase shall be rounded to the next lowest multiple of $50". Checked 2026-10-12.
`fed_senior_deduction`, `fed_senior_phaseout_single`, `fed_senior_phaseout_mfj`	Enacted schedule: 2027: `fed_senior_deduction` $6,000, `fed_senior_phaseout_single` $75,000, `fed_senior_phaseout_mfj` $150,000; 2028: `fed_senior_deduction` $6,000, `fed_senior_phaseout_single` $75,000, `fed_senior_phaseout_mfj` $150,000; 2029: `fed_senior_deduction` $0, `fed_senior_phaseout_single` $0, `fed_senior_phaseout_mfj` $0; held at the 2029 value after 2029.	The federal $6,000 senior deduction (IRC 151(d)(5)(C)), reduced by 6% of MAGI over $75,000 ($150,000 joint), flows into federal taxable income for taxable years beginning before January 1, 2029; it is 0 from 2029. Amounts are not indexed. 26 U.S.C. 151(d)(5)(C) (Deduction for seniors) (Legal Information Institute (Cornell) - U.S. Code, federal): Senior deduction and its sunset. Quoted: "in the case of a taxable year beginning before january 1, 2029, there shall be allowed a deduction in an amount equal to $6,000 for each qualified individual"; "as exceeds $75,000 ($150,000 in the case of a joint return)". Checked 2026-10-12. Book 104: 2025 Colorado Individual Income Tax Filing Guide (Colorado Department of Revenue, instructions): Colorado tax starts from federal taxable income (Form 1040 line 15), which carries the federal standard deduction, the 63(f) amounts and the senior deduction. Quoted: "Enter your federal taxable income from your federal income tax form 1040, 1040 SR, or 1040 SP, line 15.". Checked 2026-10-12.
`std_addback_agi_threshold`, `std_addback_keep_single`, `std_addback_keep_mfj`	Fixed in law: held at the rules-year amount in every later year.	Above $300,000 of AGI the federal standard or itemized deduction beyond $1,000 single / $2,000 joint is added back for 2026 and later (it was $12,000/$16,000 for 2023-2025); nominal, no indexing. Individual Income Tax Guide (Colorado Department of Revenue, agency_page): Addback threshold and 2026+ limits. Quoted: "whose adjusted gross income exceeds $300,000 and who claims either itemized deductions or the standard deduction on their federal return"; "2026 and later $1,000 $2,000". Checked 2026-10-12.
`ss_exempt_agi_single`, `ss_exempt_agi_mfj`	Fixed in law: held at the rules-year amount in every later year.	For ages 55-64 the Social Security cap rises to the full benefit when AGI is at most $75,000 single / $95,000 joint (HB24-1142, C.R.S. 39-22-104(4)(f)(III)(A)); nominal, no indexing. HB24-1142 (signed act), amending C.R.S. 39-22-104(4)(f) (Internet Archive capture) (Colorado General Assembly, legislation): AGI limits. Quoted: "less than or equal to seventy-five thousand dollars if filing individually or ninety-five thousand dollars if filing jointly". Checked 2026-09-30.
`co-pension-ss-caps` (a table held in code), `survivor_young_cap`	Fixed in law: held at the rules-year amount in every later year.	The pension and annuity subtraction is capped at $24,000 (65+) and $20,000 (55-64, and a death benefit received under 55); nominal amounts, no indexing. HB24-1142 (signed act), amending C.R.S. 39-22-104(4)(f) (Internet Archive capture) (Colorado General Assembly, legislation): Caps. Quoted: "are capped at twenty-four thousand dollars per tax year for any individual who is sixty-five years of age or older at the close of the taxable year". Checked 2026-09-30. Income Tax Topics: Social Security, Pensions, and Annuities (Jan 2025) (Colorado Department of Revenue, agency_page): Under-55 death-benefit cap. Quoted: "In this case, the amount the individual may subtract is limited to $20,000". Checked 2026-10-12.
`military_cap_young`	Enacted schedule: 2027: $15,000; 2028: $15,000; 2029: $0; held at the 2029 value after 2029.	C.R.S. 39-22-104(4)(y): a retiree under 55 may subtract military retirement pay up to $15,000 for tax years 2022 through 2028; the subtraction applies only to tax years 'prior to January 1, 2029', so it is $0 from 2029 (age 55+ uses the general pension subtraction instead). HB26-1062 (uncapped subtraction) was postponed indefinitely. Colorado Revised Statutes 2024, Title 39 (uncertified printout; Internet Archive capture), § 39-22-104(4)(y) (Colorado Office of Legislative Legal Services, statute): Military retirement subtraction amounts and sunset. Quoted: "for income tax years commencing on or after january 1, 2019, but prior to january 1, 2029, an amount equal to a qualified individual's military retirement benefits"; "fifteen thousand dollars for income tax years commencing on or after january 1, 2022, but before january 1, 2029"; ""qualified individual" means an individual who is under fifty-five years of age at the close of the taxable year". Checked 2026-09-30. Retired Servicemembers (Colorado Department of Revenue, agency_page): DOR table through 2028. Quoted: "$15,000 $15,000 $15,000 $15,000 $15,000 $15,000". Checked 2026-10-12.
`military_min_age`, `survivor_young_below_age`	Attained age: the same age in every year.	Fixed attained age 55 at the close of the tax year splits the military and pension/death-benefit rules. Retired Servicemembers (Colorado Department of Revenue, agency_page): Age wording. Quoted: "under 55 years of age at the end of the tax year". Checked 2026-10-12. Income Tax Topics: Social Security, Pensions, and Annuities (Jan 2025) (Colorado Department of Revenue, agency_page): Age wording. Quoted: "Individual taxpayers under age 55 may not claim the subtraction unless the pension and annuity income is a death benefit". Checked 2026-10-12.
`cap_loss_limit`, `cap_loss_limit_mfs`	Fixed in law: held at the rules-year amount in every later year.	Colorado starts from federal taxable income, so the fixed IRC 1211(b) limit applies. 26 U.S.C. 1211 (Limitation on capital losses) (Legal Information Institute (Cornell) - U.S. Code, federal): IRC 1211(b) limits a non-corporate capital loss against other income to $3,000 ($1,500 MFS), with no inflation adjustment. Quoted: "(1) $3,000 ($1,500 in the case of a married individual filing a separate return), or". Checked 2026-10-12.

Enacted for later years, not applied by the projection

The under-55 military retirement subtraction (up to $15,000) ends after tax year 2028. (2029+)
- C.R.S. 2024 Title 39, § 39-22-104(4)(y) (Colorado Office of Legislative Legal Services, statute): Sunset. Quoted: "but before january 1, 2029". Checked 2026-09-30.

What the engine does not calculate, and known approximations

A Roth conversion (a traditional IRA distribution on Form 1040 line 4b, never premature) draws the pension and annuity subtraction after the other distributions, within the cap: the reading of the Department's own list of qualifying income, which does not name conversions (engine 1.8.0, DIFF-CO-01).
The PERA/DPSRS contribution-basis subtraction is not modeled. (Public pensions)
The child tax credit, the Family Affordability credit and the child care credit are refundable (or need expenses) and are not calculated. Sources: IRS releases tax inflation adjustments for tax year 2026, including amendments from the One, Big, Beautiful Bill (checked 2026-10-12); Book 104 2025 Colorado Individual Income Tax Filing Guide (checked 2026-10-12); Individual Income Tax Guide (checked 2026-10-12); IRS releases tax inflation adjustments for tax year 2026 (checked 2026-10-12); 26 U.S.C. § 151 (checked 2026-10-12); Child Tax Credit & Earned Income Tax Credit (web page) (checked 2026-10-12); 2025 DR 0104TN Colorado EITC for ITIN Filers or Certain Filers Under Age 25 (checked 2026-10-12).
The disability assistance credit (a refundable credit for a filer with a full year of disability benefits and low income) is not calculated: it depends on the source of the benefits and an income test the inputs do not carry. Sources: Rev. Proc. 2025-32 (2026 inflation adjustments) (checked 2026-10-12).
The Social Security subtraction for benefits received under age 55 because of the death of the person entitled to them is calculated only when socialSecuritySurvivor says so (engine 1.8.0): without it such benefits are taxed. Sources: Income Tax Topics: Social Security, Pensions, and Annuities (Revised January 2025) (checked 2026-10-12); HB24-1142 Social Security Income Tax Subtraction (checked 2026-10-12); SB25-136 (2025 Regular Session) bill page (checked 2026-10-12); HB24-1142 (signed act; Internet Archive capture) (checked 2026-09-28).
Subtractions for state income tax refunds, interest on United States government obligations, family and medical leave insurance benefits, charitable contributions of filers who do not itemize, CollegeInvest and Colorado ABLE contributions, qualified reservation income and active-duty pay after reacquiring Colorado residency are not calculated: the inputs do not separate these amounts. Sources: Book 104 2025 Colorado Individual Income Tax Filing Guide (checked 2026-10-12).
Additions for other states' bond interest and for nonqualified CollegeInvest or Colorado ABLE distributions are not calculated: that income is not among the inputs. Sources: Book 104 2025 Colorado Individual Income Tax Filing Guide (checked 2026-10-12).

What the engine does not calculate for any state (itemized deductions, credits beyond those listed, part-year residents, and more) is listed on the calculation order page.

Verification

Worksheet-tested Golden and unit tests follow form DR 0104 line 1 (federal taxable income) and DR 0104AD line 4 (the pension and Social Security subtraction).

Golden scenarios (hand-computed expected tax, asserted to within $1): M13, GCO3, COSEN1, COCONV1.
State-specific unit tests: test_co_ss_hb24_1142_age_and_agi, test_co_shared_20k_cap_ss_and_pension, test_v3_folds_v2, test_co_under55_no_subtraction, test_d12_conformity_states, test_co_conversion_not_pooled, test_compute_federal, test_compute_federal_ss_parts, test_co_one_military_subtraction, test_c_interface_edges, test_replay_co_rp, test_applied, test_400s, test_paths, test_co_per_spouse_household_split, test_legacy_request_equals_v2, test_equal_ages_reproduce_household, test_military_tiers, test_co_per_spouse, test_ratio_rules, test_co_per_spouse_household, test_hoh_and_credit_gaps, test_conformity_component_path.
Structural tests covering every state: 9.
State forms and worksheets followed in the test derivations: DR 0104 line 1; DR 0104AD line 4; DR 0104AD lines 4 and 7: one subtraction for a young survivor's military retirement pay (engine 1.8.0).