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District of Columbia state income tax: engine rules, 2026

How the QuantCalc engine computes District of Columbia 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 · Social Security · IRA, 401(k) and private pensions · Public pensions · Military retirement pay · Roth conversions · Capital gains · 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 DC).

How the tax is computed

Every step the engine takes for District of Columbia, 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 District of Columbia'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):

SingleMarried filing jointlyMarried filing separatelyHead of household
Rate schedule usedsingle schedulejoint schedulesingle schedulesingle schedule
Top rate10.75% from $1,000,00010.75% from $1,000,00010.75% from $1,000,00010.75% from $1,000,000
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 exemptionnonenonenonenone
Age subtractions at 70 (joint: both 70)nonenonenonenone
  1. 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.
  2. 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.
  3. 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.
    District of Columbia's values · engine step (select_brackets). Sources (Rate schedule): 2026 D-40ES Estimated Payment for Individual Income Tax (booklet) (checked 2026-10-12); D.C. Code §47-1806.03 - Tax on residents and nonresidents: imposition and rates (checked 2026-10-12)
  4. 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).
    District of Columbia's values · engine step (select_brackets). Sources (Rate schedule): 2026 D-40ES Estimated Payment for Individual Income Tax (booklet) (checked 2026-10-12); D.C. Code §47-1806.03 - Tax on residents and nonresidents: imposition and rates (checked 2026-10-12)
  5. 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.
    District of Columbia's values · engine step (select_brackets). Sources (Rate schedule): 2026 D-40ES Estimated Payment for Individual Income Tax (booklet) (checked 2026-10-12); D.C. Code §47-1806.03 - Tax on residents and nonresidents: imposition and rates (checked 2026-10-12)
  6. 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.
  7. 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.
  8. Disability pay 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) Each person's disability pay (the caller's disabilityIncome, part of the pension income) is excluded up to the state's cap (all of it where there is none), for a totally and permanently disabled person where the state requires it and below the age where there is one; on a joint return without per-person amounts the cap is doubled only when a second person can qualify (the spouse also said to be disabled where the state requires it). Where the state reduces it, the total is reduced dollar for dollar by the return's income over the threshold (one threshold per return; the separate-return threshold where there is one). The excluded dollars leave the base before any retirement exclusion. Where the state reads it, the plan's minimum retirement age (when given) replaces the age at which the pay stops being excluded.
    District of Columbia's values · engine step (compute_state_tax_detail). Sources (Blindness and disability): 2026 D-40ES (checked 2026-10-12); Rev. Proc. 2025-32 (2026 inflation adjustments) (checked 2026-10-12); 2025 D-40 booklet (archived copy) (checked 2026-09-27); DC Office of Tax and Revenue: 2025_D-2440_Form_012626.pdf (checked 2026-10-12)
  9. Federal survivor annuity of a survivor at 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) A survivor at or above the age excludes the whole federal government survivor annuity (the civil service annuity received as a survivor): each spouse's own annuity by the caller's split, else equally; on the household path the filer's.
    District of Columbia's values · engine step (compute_state_tax_detail). Sources (Public pensions): D.C. Code §47-1803.02 - Gross income: items included and excluded (checked 2026-10-12); D.C. Code §47-1803.02 (gross income exclusions) (checked 2026-10-12)
  10. 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.
  11. 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.
    District of Columbia's values · engine step (compute_state_tax_detail). Sources (Military retirement pay): 47 1803.02 (checked 2026-10-12)
  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).
    District of Columbia's values · engine step (compute_state_tax_detail). Sources (Capital gains): 2025 D-40 Booklet (checked 2026-10-12); 2026 D40ES Book wLinks04012026 (checked 2026-10-12); 2025 D-40 Individual Income Tax Forms and Instructions (checked 2026-10-12); 2025 Schedule D (Form 1040), Capital Gains and Losses (checked 2026-10-12)
  13. Social Security exempt None of the federally taxable benefit enters the base.
    District of Columbia's values · engine step (ss_amount_in_state_base). Sources (Social Security): 2025 D-40 Booklet (checked 2026-10-12); D.C. Code §47-1803.02 - Gross income: items included and excluded (checked 2026-10-12); 2026 D40ES Book wLinks04012026 (checked 2026-10-12)
  14. Retirement exclusion (household) The distributions eligible for the exclusion go through the exclusion below. Taxable public-pension dollars left by a cap are not eligible; below the IRA age only employer-plan dollars are.
    District of Columbia's values · engine step (compute_state_tax_detail). Sources (IRA, 401(k) and private pensions): 2025 D-40 Booklet (checked 2026-10-12)
  15. Conversion taxed or exempt In full-exclusion states a conversion is exempt at the qualifying age (at any age where the state says so). Elsewhere, unless pooled above, it is ordinary income taxed in full.
    District of Columbia's values · engine step (compute_state_tax_detail). Sources (Roth conversions): 2025 D-40 Booklet (checked 2026-10-12)
  16. 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.
    District of Columbia's values · engine step (compute_state_tax_detail). Sources (Capital gains): 2025 D-40 Booklet (checked 2026-10-12); 2026 D40ES Book wLinks04012026 (checked 2026-10-12); 2025 D-40 Individual Income Tax Forms and Instructions (checked 2026-10-12); 2025 Schedule D (Form 1040), Capital Gains and Losses (checked 2026-10-12)
  17. 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.
    District of Columbia's values · engine step (compute_state_tax_detail). Sources (Deductions, exemptions and credits): 2026 D-40ES Estimated Payment for Individual Income Tax (booklet) (checked 2026-10-12); D.C. Code §47-1801.04 - General definitions (standard deduction, paragraph (44)) (checked 2026-10-12); 2025 D-40 Booklet (checked 2026-10-12); D.C. Code 47-1806.04 (credits) (checked 2026-10-12); D.C. Law 26-89, D.C. Income and Franchise Tax Conformity and Revision Temporary Amendment Act of 2025 (checked 2026-10-12); B26-0458 Signed Act (D.C. Act 26-217), temporary conformity act (checked 2026-10-12); EITC FAQs (checked 2026-10-12); DC EITC (checked 2026-10-12); D.C. Law 26-55, Fiscal Year 2026 Budget Support Act of 2025 (D.C. Law Library) (checked 2026-10-12); D.C. Code § 47-1806.06 Credits - Property taxes (checked 2026-10-12)
  18. 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.
    District of Columbia's values · engine step (compute_state_tax_detail). Sources (Blindness and disability): 2026 D-40ES (checked 2026-10-12); Rev. Proc. 2025-32 (2026 inflation adjustments) (checked 2026-10-12); 2025 D-40 booklet (archived copy) (checked 2026-09-27); DC Office of Tax and Revenue: 2025_D-2440_Form_012626.pdf (checked 2026-10-12)
  19. Income exclusion for disability only when the caller says a person is blind or disabled Up to the amount of income for each disabled person, while the income total is under the limit, taken against the base (the engine does not know each person's own income; taxable income cannot go below zero).
    District of Columbia's values · engine step (compute_state_tax_detail). Sources (Blindness and disability): 2026 D-40ES (checked 2026-10-12); Rev. Proc. 2025-32 (2026 inflation adjustments) (checked 2026-10-12); 2025 D-40 booklet (archived copy) (checked 2026-09-27); DC Office of Tax and Revenue: 2025_D-2440_Form_012626.pdf (checked 2026-10-12)
  20. 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.
  21. 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.
  22. Separate-return scaling married filing separately For the halved-joint rule, taxable income is doubled before the schedule and the result halved.
    District of Columbia's values · engine step (compute_state_tax_detail). Sources (Rate schedule): 2026 D-40ES Estimated Payment for Individual Income Tax (booklet) (checked 2026-10-12); D.C. Code §47-1806.03 - Tax on residents and nonresidents: imposition and rates (checked 2026-10-12)
  23. 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.
    District of Columbia's values · engine step (apply_state_brackets). Sources (Rate schedule): 2026 D-40ES Estimated Payment for Individual Income Tax (booklet) (checked 2026-10-12); D.C. Code §47-1806.03 - Tax on residents and nonresidents: imposition and rates (checked 2026-10-12)
  24. 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.
  25. 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).
    District of Columbia's values · engine step (state_tax_effective_config). Sources (Rate schedule): 2026 D-40ES Estimated Payment for Individual Income Tax (booklet) (checked 2026-10-12); D.C. Code §47-1806.03 - Tax on residents and nonresidents: imposition and rates (checked 2026-10-12)
  26. 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.
    District of Columbia's values · engine step (compute_state_tax_detail). Sources (Social Security): 2025 D-40 Booklet (checked 2026-10-12); D.C. Code §47-1803.02 - Gross income: items included and excluded (checked 2026-10-12); 2026 D40ES Book wLinks04012026 (checked 2026-10-12)
  27. 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.
    District of Columbia's values · engine step (compute_state_tax_detail). Sources (Capital gains): 2025 D-40 Booklet (checked 2026-10-12); 2026 D40ES Book wLinks04012026 (checked 2026-10-12); 2025 D-40 Individual Income Tax Forms and Instructions (checked 2026-10-12); 2025 Schedule D (Form 1040), Capital Gains and Losses (checked 2026-10-12)
  28. 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).
    District of Columbia's values · engine step (compute_state_tax_detail). Sources (Social Security): 2025 D-40 Booklet (checked 2026-10-12); D.C. Code §47-1803.02 - Gross income: items included and excluded (checked 2026-10-12); 2026 D40ES Book wLinks04012026 (checked 2026-10-12)
  29. 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).
    District of Columbia's values · engine step (state_tax_refundable_credits). Sources (Deductions, exemptions and credits): 2026 D-40ES Estimated Payment for Individual Income Tax (booklet) (checked 2026-10-12); D.C. Code §47-1801.04 - General definitions (standard deduction, paragraph (44)) (checked 2026-10-12); 2025 D-40 Booklet (checked 2026-10-12); D.C. Code 47-1806.04 (credits) (checked 2026-10-12); D.C. Law 26-89, D.C. Income and Franchise Tax Conformity and Revision Temporary Amendment Act of 2025 (checked 2026-10-12); B26-0458 Signed Act (D.C. Act 26-217), temporary conformity act (checked 2026-10-12); EITC FAQs (checked 2026-10-12); DC EITC (checked 2026-10-12); D.C. Law 26-55, Fiscal Year 2026 Budget Support Act of 2025 (D.C. Law Library) (checked 2026-10-12); D.C. Code § 47-1806.06 Credits - Property taxes (checked 2026-10-12)

Rate schedule

Single

Taxable income fromtoRate
$0$10,0004%
$10,000$40,0006%
$40,000$60,0006.5%
$60,000$250,0008.5%
$250,000$500,0009.25%
$500,000$1,000,0009.75%
$1,000,000and up10.75%

Married filing jointly uses the same thresholds as single.

Head of household uses the single schedule.

Married filing separately: one schedule applies to every filing status, so the engine uses it unscaled with the single deduction.

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.

Social Security

Social Security benefits are fully exempt: none of the federally taxable amount enters the state base.

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

IRA, 401(k) and private pensions

  • No exclusion: pension, annuity and IRA/401(k) distributions are taxed as ordinary income.

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):

Military retirement pay

  • No military-specific rule: military retirement pay is pension income under the general retirement rules above.
  • Rules are applied per taxpayer at that person's own age when the spouse's age is given. API value: rules.militaryRetirement.treatment: "taxable_as_pension".

Roth conversions

A conversion is taxed as ordinary income in full. It does not draw any retirement-income exclusion.

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

Capital gains

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

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

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.
  • Up to $10,000 of income is excluded for each disabled person while the income total is under $100,000.
  • The API applies these through its blind, disabled, spouse.blind and spouse.disabled fields; absent means false.

Part-year and nonresident returns

  • Part-year resident (D-40 (part-year)): the tax on the state's own income (what was received while a resident, plus the state-source income while a nonresident), with the deductions and exemptions the form prorates scaled by its ratio (prorated by days).
  • Nonresident (none (not subject to DC income tax)): no tax.
  • 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 4 places, at most 1.
  • Prorated on a part-year return: the standard deduction.
  • Part-year: the standard deduction × the days domiciled / 365. A nonresident is not subject to the DC income tax.
  • 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.

SpousesDistrict of Columbia's rule
One spouse a full-year resident, the other a part-year residentthe couple's choice: a joint part-year / nonresident return or separate returns; the joint return is not calculated: the D-40 instructions give a joint return's line 4 as both spouses' total federal AGI and do not say how a joint return apportions a part-year or nonresident spouse's income (DC taxes a nonresident's income not at all).
One spouse a full-year resident, the other a nonresidentthe couple's choice: a joint part-year / nonresident return or separate returns; the joint return is not calculated: the D-40 instructions give a joint return's line 4 as both spouses' total federal AGI and do not say how a joint return apportions a part-year or nonresident spouse's income (DC taxes a nonresident's income not at all).
One spouse a part-year resident, the other a nonresidentthe couple's choice: a joint part-year / nonresident return or separate returns; the joint return is not calculated: the D-40 instructions give a joint return's line 4 as both spouses' total federal AGI and do not say how a joint return apportions a part-year or nonresident spouse's income (DC taxes a nonresident's income not at all).
Both part-year residents, different resident periodsseparate returns is required.
Both nonresidents, only one with income from the statea joint part-year / nonresident return is required.

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$2,645.25
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$4,732.50
Single, 60: $60,000 other ordinary income and a $50,000 Roth conversion$6,381.50
Married filing jointly, 66: $30,000 IRA, a $40,000 Roth conversion, $30,000 Social Security ($25,500 federally taxable)$1,870
Single, 58: $36,000 military retirement pay and $30,000 wages$2,843.50
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$1,369

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: $2,645.25
LineAmount
Income total used by the income tests$82,000
+ Other ordinary income in the base$10,000
+ Retirement income in the base$50,000
+ Long-term gain in the base$5,000
− Standard deduction$18,150
= State taxable income$46,850
Tax from the rate schedule$2,645.25
= Tax before credits$2,645.25
= Tax$2,645.25
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: $4,732.50
LineAmount
Income total used by the income tests$144,000
+ Other ordinary income in the base$20,000
+ Retirement income in the base$80,000
+ Long-term gain in the base$10,000
− Standard deduction$35,500
= State taxable income$74,500
Tax from the rate schedule$4,732.50
= Tax before credits$4,732.50
= Tax$4,732.50
Single, 60: $60,000 other ordinary income and a $50,000 Roth conversion: $6,381.50
LineAmount
Income total used by the income tests$110,000
+ Other ordinary income in the base$60,000
+ Roth conversion in the base$50,000
− Standard deduction$16,100
= State taxable income$93,900
Tax from the rate schedule$6,381.50
= Tax before credits$6,381.50
= Tax$6,381.50
Married filing jointly, 66: $30,000 IRA, a $40,000 Roth conversion, $30,000 Social Security ($25,500 federally taxable): $1,870
LineAmount
Income total used by the income tests$95,500
+ Retirement income in the base$30,000
+ Roth conversion in the base$40,000
− Standard deduction$35,500
= State taxable income$34,500
Tax from the rate schedule$1,870
= Tax before credits$1,870
= Tax$1,870
Single, 58: $36,000 military retirement pay and $30,000 wages: $2,843.50
LineAmount
Income total used by the income tests$66,000
+ Other ordinary income in the base$30,000
+ Retirement income in the base$36,000
− Standard deduction$16,100
= State taxable income$49,900
Tax from the rate schedule$2,843.50
= Tax before credits$2,843.50
= Tax$2,843.50
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: $1,369
LineAmount
Income total used by the income tests$85,500
+ Other ordinary income in the base$10,000
+ Retirement income in the base$50,000
− Standard deduction$33,850
= State taxable income$26,150
Tax from the rate schedule$1,369
= Tax before credits$1,369
= Tax$1,369

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 District of Columbia's law moves it. Rates and the rules themselves stay the 2026 ones (how projection works).

Amounts (engine fields)After 2026What the law says, and the source
brackets_single (the single rate schedule's thresholds), brackets_mfj (the mfj rate schedule's thresholds)Fixed in law: held at the rules-year amount in every later year.For tax years after 2021 the seven-bracket table in § 47-1806.03(a)(11) is nominal ($10,000 / $40,000 / $60,000 / $250,000 / $500,000 / $1,000,000); the section has no indexing.
  • D.C. Code § 47-1806.03 (Council of the District of Columbia (D.C. Law Library), statute): Rate table (a)(11). Quoted: "over $250,000 but not over $500,000 $19,650, plus 9.25% of the excess over $250,000"; "over $1,000,000 $91,525, plus 10.75% of the excess over $1,000,000". Checked 2026-10-12.
std_deduction_single, std_deduction_mfj, std_deduction_hohTied to an indexed federal amount: IRC 63(c)(2) basic standard deduction, indexed under IRC 63(c)(7)/(4) by the IRC 1(f)(3) cost-of-living adjustment (chained CPI-U); the increase rounded down to a multiple of $50.D.C. Code 47-1801.04(44)(A)(iv), (B)(iv), (C)(iv): for taxable years after 2017 the standard deduction is the one prescribed in IRC 63(c), so the basic amounts are the federal ones, indexed federally (increases rounded down to $50). Temporary D.C. Law 26-89 decoupled them for 2025-2026 at $15,000 / $22,500 / $30,000 with DC CPI indexing, but it expired about September 25, 2026 and the Code as codified on 2026-09-30 carries only the federal rule; OTR's 2026 estimated-tax booklet uses the federal $16,100, as the engine does.
  • D.C. Code § 47-1801.04 (Council of the District of Columbia (D.C. Law Library), statute): Definition (44) as codified on 2026-09-30: for taxable years after 2017 the DC standard deduction is the IRC 63(c) standard deduction (basic plus the additional amounts); the 2026 decoupling (D.C. Law 26-89) is recorded only as expired temporary legislation. Quoted: "(iv) for taxable years beginning after december 31, 2017, the standard deduction as prescribed in section 63(c) of the internal revenue code of 1986"; "income and franchise tax conformity and revision temporary amendment act of 2025". 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.
  • 2026 D-40ES Estimated Payment booklet (DC Office of Tax and Revenue, instructions): OTR 2026 estimated-tax instructions. Quoted: "enter $16,100 if single". Checked 2026-10-12.
std_deduction_aged_add_unmarried, std_deduction_aged_add_married, blind_std_add_unmarried, blind_std_add_marriedTied to an indexed federal amount: IRC 63(f) additional standard deduction for age/blindness, indexed under IRC 63(c)(4) by the IRC 1(f)(3) cost-of-living adjustment (chained CPI-U, Sept-Aug average); the increase rounded down to a multiple of $50.The DC standard deduction is the one 'prescribed in section 63(c)' of the IRC, which includes the 63(f) additional amounts for age and blindness, so these are the federal amounts, indexed federally (increases rounded down to $50).
  • D.C. Code § 47-1801.04 (Council of the District of Columbia (D.C. Law Library), statute): Definition (44) as codified on 2026-09-30: for taxable years after 2017 the DC standard deduction is the IRC 63(c) standard deduction (basic plus the additional amounts); the 2026 decoupling (D.C. Law 26-89) is recorded only as expired temporary legislation. Quoted: "(iv) for taxable years beginning after december 31, 2017, the standard deduction as prescribed in section 63(c) of the internal revenue code of 1986"; "income and franchise tax conformity and revision temporary amendment act of 2025". 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.
disabled_income_exclusion, disabled_income_exclusion_agi_limitFixed in law: held at the rules-year amount in every later year.Up to $10,000 of income for a person the SSA has determined permanently and totally disabled, household AGI under $100,000; nominal in § 47-1803.02(a)(2)(V), no indexing.
  • D.C. Code § 47-1803.02 (Council of the District of Columbia (D.C. Law Library), statute): Exclusion (V). Quoted: "income derived from any source, not to exceed $10,000, for a person who has been determined to have a permanent and total disability"; "is less than $100,000". Checked 2026-10-12.
dis_income_cap, dis_income_reduce_overFixed in law: held at the rules-year amount in every later year.Disability pay excludable under former IRC 105(d) as before the 1983 repeal ($5,200 a year, reduced over $15,000); frozen, no indexing.
  • D.C. Code § 47-1803.02 (Council of the District of Columbia (D.C. Law Library), statute): Exclusion (M). Quoted: "certain disability income payments excludable under". Checked 2026-10-12.
  • 2025 Form D-2440 Disability Income Exclusion (DC Office of Tax and Revenue, instructions): Amounts. Quoted: "The maximum annual exclusion per disabled person is $5,200"; "$15,000 is the amount DC uses to reduce the disability income you can exclude". Checked 2026-10-12.
dis_income_max_ageAttained age: the same age in every year.Only for a person under 65 at the end of the year (former IRC 105(d)); fixed age.
survivor_fcs_exempt_min_ageAttained age: the same age in every year.Survivor benefits from DC or the federal government are excluded for persons 62 or older by the end of the taxable year; fixed age.
  • D.C. Code § 47-1803.02 (Council of the District of Columbia (D.C. Law Library), statute): Exclusion (N)(ii). Quoted: "survivor benefits received from the district of columbia or the federal government by persons who are 62 years of age or older by the end of the taxable year". Checked 2026-10-12.
cap_loss_limit, cap_loss_limit_mfsFixed in law: held at the rules-year amount in every later year.DC starts from federal AGI, 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.
dc-credits (a table held in code)Indexed: Washington-area CPI (DC OTR annual adjustment); the increase rounded to the nearest $1. The engine carries the 2025 figure (the latest published) for 2026, so a projection adds 1 year of indexing at the factor's average annual rate.D.C. Code 47-1806.06 and 47-1806.04(f)(1)(C): the Schedule H maximum and eligibility threshold and the childless EITC amounts are increased annually by the Washington-area CPI; the engine carries the 2025 amounts.
  • 2025 D-40 Individual Income Tax Forms and Instructions booklet (Revised 11/2025; file version 08/2026) (DC Office of Tax and Revenue (OCFO), agency_page): DC Schedule H homeowner/renter property tax credit, 2025: percentage bands for claimants under 70, including the band above the statutory $55,000 Quoted: "The maximum credit increases to $1,425. The income limits"; "increase to $66,000 for people under 70 and $90,000 for people 70 or older.". Checked 2026-10-12.
  • 2025 D-40 Individual Income Tax Booklet (DC Office of Tax and Revenue, agency_page): DC EITC: % of federal EIC (with child) / own childless schedule Quoted: "The District EITC is now 100% of the federal EITC"; "Line 27d Multiply the calculated federal EIC amount x 1.00 and enter". Checked 2026-10-12.
  • D.C. Code 47-1806.04 (credits) (Council of the District of Columbia (code.dccouncil.gov), statute): DC EITC: % of federal EIC (with child) / own childless schedule Quoted: "in an amount equal to 85% of the earned income tax credit allowed under section 32"; "beginning after December 31, 2028, an individual with a qualifying child". Checked 2026-10-12.

Enacted for later years, not applied by the projection

None found: the research found no change enacted for years after 2026 beyond the schedules above.

What the engine does not calculate, and known approximations

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 An engine 1.2.0 test follows the 2026 D-40ES head-of-household deduction; golden rows pin the schedule.