State tax docs / States / Oklahoma

Oklahoma state income tax: engine rules, 2026

How the QuantCalc engine computes Oklahoma 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 · 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 OK).

How the tax is computed

Every step the engine takes for Oklahoma, 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 Oklahoma'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	head-of-household schedule
Top rate	4.5% from $7,200	4.5% from $14,400	4.5% from $7,200	4.5% from $14,400
Standard deduction, under 65	$6,350	$12,700	$6,350	$9,350
Standard deduction at 70 (joint: both 70)	$6,350	$12,700	$6,350	$9,350
Personal exemption	$1,000	$2,000	$1,000	$1,000
Age subtractions at 70 (joint: both 70)	$1,000	$2,000	$1,000	$1,000

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.
Oklahoma's values · engine step (select_brackets). Sources (Rate schedule): Enrolled House Bill No. 2764 (2025) (checked 2026-10-12); 2026 Oklahoma Income Tax Withholding Tables (Packet OW-2) (checked 2026-10-12); 2025 Form 511 Packet (Oklahoma resident income tax) (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).
Oklahoma's values · engine step (select_brackets). Sources (Rate schedule): Enrolled House Bill No. 2764 (2025) (checked 2026-10-12); 2026 Oklahoma Income Tax Withholding Tables (Packet OW-2) (checked 2026-10-12); 2025 Form 511 Packet (Oklahoma resident income tax) (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.
Oklahoma's values · engine step (select_brackets). Sources (Rate schedule): Enrolled House Bill No. 2764 (2025) (checked 2026-10-12); 2026 Oklahoma Income Tax Withholding Tables (Packet OW-2) (checked 2026-10-12); 2025 Form 511 Packet (Oklahoma resident income tax) (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.
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.
Oklahoma's values · engine step (compute_state_tax_detail). Sources (Military retirement pay): 511 Pkt (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.
Oklahoma's values · engine step (military_exempt_one). Sources (Military retirement pay): 511 Pkt (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).
Oklahoma's values · engine step (compute_state_tax_detail). Sources (Capital gains): 2025 Oklahoma Resident Individual Income Tax Forms and Instructions (Form 511 Packet) (checked 2026-10-12); Form 511 Packet (checked 2026-10-12); 2025 Schedule D (Form 1040), Capital Gains and Losses (checked 2026-10-12)
Non-covered public pension excluded in full only when the caller says the pension was not covered by Social Security Only when the caller says the public pension was not covered by Social Security: the pension takes the uncapped public-pension exemption below (per taxpayer, without using the general retirement exclusion).
Oklahoma's values · engine step (compute_state_tax_detail). Sources (Public pensions): 2025 Oklahoma Resident Individual Income Tax Forms and Instructions (Form 511 Packet) (checked 2026-10-12)
Social Security exempt None of the federally taxable benefit enters the base.
Oklahoma's values · engine step (ss_amount_in_state_base). Sources (Social Security): 2025 Oklahoma Resident Individual Income Tax Forms and Instructions (Form 511 Packet) (checked 2026-10-12)
Does a conversion draw the retirement cap? Where the state lets a conversion draw the capped exclusion, and the filer is at or above the conversion age (the state's own pooling age where it has one; any age for a disabled person where the state says so), the conversion is pooled with distributions against the cap. A spouse who elects not to claim the exclusion draws none of it.
Oklahoma's values · engine step (compute_state_tax_detail). Sources (Roth conversions): 2025 Oklahoma Resident Individual Income Tax Forms and Instructions (Form 511 Packet) (checked 2026-10-12)
Retirement exclusion per spouse (both ages known) joint returns with the spouse's age given Full-exclusion states exclude each qualifying spouse's own dollars. Capped states give each spouse the single cap for their own age against their own eligible dollars (pension dollars only where the exclusion is pension-only; employer dollars only below the IRA age), less their military exclusion and their own Social Security offset (by the spouse's stated gross benefits, else half). Per-return states (and the pooled-if-both-qualify rule when both qualify) apply the joint cap to the couple's pooled eligible dollars when either spouse qualifies. The income tests then apply once to the summed deduction.
Oklahoma's values · engine step (compute_state_tax_detail). Sources (IRA, 401(k) and private pensions): 2025 Oklahoma Resident Individual Income Tax Forms and Instructions (Form 511 Packet) (checked 2026-10-12)
Conversion pooled with distributions The conversion joins the distributions against the one cap (with a spouse split in a per-taxpayer state, each spouse's own distributions and conversion against that spouse's cap). Nothing of the conversion is added separately.
Oklahoma's values · engine step (compute_state_tax_detail). Sources (Roth conversions): 2025 Oklahoma Resident Individual Income Tax Forms and Instructions (Form 511 Packet) (checked 2026-10-12)
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.
Oklahoma's values · engine step (compute_state_tax_detail). Sources (IRA, 401(k) and private pensions): 2025 Oklahoma Resident Individual Income Tax Forms and Instructions (Form 511 Packet) (checked 2026-10-12)
Retirement exclusion per spouse (declared split) joint returns with each spouse's own amounts given With a spouse split in a per-taxpayer state, each spouse's own eligible dollars draw that spouse's single cap (less their military exclusion); an income limit then applies once to the sum.
Oklahoma's values · engine step (compute_state_tax_detail). Sources (IRA, 401(k) and private pensions): 2025 Oklahoma Resident Individual Income Tax Forms and Instructions (Form 511 Packet) (checked 2026-10-12)
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.
Oklahoma's values · engine step (compute_state_tax_detail). Sources (Roth conversions): 2025 Oklahoma Resident Individual Income Tax Forms and Instructions (Form 511 Packet) (checked 2026-10-12)
Cap by age tier The full cap at or above the exclusion age, the lower cap at or above the partial age, otherwise none. Joint returns use the joint cap; every other status the single cap.
Oklahoma's values · engine step (retirement_distributions_in_state_base). Sources (IRA, 401(k) and private pensions): 2025 Oklahoma Resident Individual Income Tax Forms and Instructions (Form 511 Packet) (checked 2026-10-12)
The capped deduction Deduction = the smaller of the eligible distributions and the cap, then reduced by the income limit above; the rest of the distributions stays in the base.
Oklahoma's values · engine step (retirement_distributions_in_state_base). Sources (IRA, 401(k) and private pensions): 2025 Oklahoma Resident Individual Income Tax Forms and Instructions (Form 511 Packet) (checked 2026-10-12)
One taxpayer's cap joint returns with the spouse's age given For per-spouse calculations, each spouse's cap is the single-column cap for their age tier.
Oklahoma's values · engine step (per_taxpayer_cap_single). Sources (IRA, 401(k) and private pensions): 2025 Oklahoma Resident Individual Income Tax Forms and Instructions (Form 511 Packet) (checked 2026-10-12)
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.
Oklahoma's values · engine step (compute_state_tax_detail). Sources (Capital gains): 2025 Oklahoma Resident Individual Income Tax Forms and Instructions (Form 511 Packet) (checked 2026-10-12); Form 511 Packet (checked 2026-10-12); 2025 Schedule D (Form 1040), Capital Gains and Losses (checked 2026-10-12)
Personal exemption The joint amount on a joint return, the head-of-household amount where set, otherwise the single amount.
Oklahoma's values · engine step (compute_state_tax_detail). Sources (Deductions, exemptions and credits): 2025 Oklahoma Resident Individual Income Tax Forms and Instructions (Form 511 Packet) (checked 2026-10-12); 2026 Oklahoma Income Tax Withholding Tables (Packet OW-2) (checked 2026-10-12); IRS Revenue Procedure 2025-32 (2026 inflation adjustments) (checked 2026-10-12); 2025 Form 511-EIC Oklahoma Earned Income Credit Worksheet (with 2020 EIC Table) (checked 2026-10-12); Rev. Proc. 2019-44 (2020 inflation adjustments), section 3.07 Earned Income Credit (checked 2026-10-12); 26 U.S.C. 32 (United States Code, 2020 edition) (checked 2026-10-12); 2025 Form 538-H Claim for Credit or Refund of Property Tax (checked 2026-10-12)
Exemption for blindness only when the caller says a person is blind or disabled An extra exemption for each blind person (the filer, and the spouse on a joint return). Where the state's exemption is for a person who is blind or disabled, a disabled person below the state's age limit (if any) qualifies too, one exemption per person either way.
Oklahoma's values · engine step (compute_state_tax_detail). Sources (Blindness and disability): 2025 Form 511 packet (checked 2026-10-12)
Dependent exemptions and deductions only when the caller lists dependents An amount per dependent subtracted like the personal exemption: the state's flat amount, or the stepped per-exemption amount the filer gets, or the state's own income steps; nothing above an income limit where there is one; a percentage phase-out per income step where there is one; one more for a dependent in an age band or a student up to an age, for a dependent born in the year, and for a disabled dependent; a deduction per dependent beyond the first on joint and head-of-household returns; and a child deduction by an income table for dependents under an age. A head of household's status exemption that already holds one dependent's amount counts one fewer. Where the state says so, the phase-out is measured on the state AGI (the base before deductions).
Oklahoma's values · engine step (compute_state_tax_detail). Sources (Deductions, exemptions and credits): 2025 Oklahoma Resident Individual Income Tax Forms and Instructions (Form 511 Packet) (checked 2026-10-12); 2026 Oklahoma Income Tax Withholding Tables (Packet OW-2) (checked 2026-10-12); IRS Revenue Procedure 2025-32 (2026 inflation adjustments) (checked 2026-10-12); 2025 Form 511-EIC Oklahoma Earned Income Credit Worksheet (with 2020 EIC Table) (checked 2026-10-12); Rev. Proc. 2019-44 (2020 inflation adjustments), section 3.07 Earned Income Credit (checked 2026-10-12); 26 U.S.C. 32 (United States Code, 2020 edition) (checked 2026-10-12); 2025 Form 538-H Claim for Credit or Refund of Property Tax (checked 2026-10-12)
Extra exemption at 65 for low income One more exemption per taxpayer at or above the age when the income total (conversions left out where the state says so) is at most the filing status's limit.
Oklahoma's values · engine step (compute_state_tax_detail). Sources (Age 65+ subtractions and credits): 2025 Form 511 Packet (Oklahoma resident income tax) (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.
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.
Oklahoma's values · engine step (compute_state_tax_detail). Sources (Rate schedule): Enrolled House Bill No. 2764 (2025) (checked 2026-10-12); 2026 Oklahoma Income Tax Withholding Tables (Packet OW-2) (checked 2026-10-12); 2025 Form 511 Packet (Oklahoma resident income tax) (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.
Oklahoma's values · engine step (apply_state_brackets). Sources (Rate schedule): Enrolled House Bill No. 2764 (2025) (checked 2026-10-12); 2026 Oklahoma Income Tax Withholding Tables (Packet OW-2) (checked 2026-10-12); 2025 Form 511 Packet (Oklahoma resident income tax) (checked 2026-10-12)
Child credits only when the caller lists dependents A credit per dependent at or under the child age and another per older dependent; none above an income limit where there is one; where the credit is a share of the federal child tax credit, the share of the federal credit the household is allowed (the nonrefundable part up to the federal tax, the refundable part from earned income); reduced per dollar over a threshold, or by a percentage per thousand dollars over a start, where the state says so. Also a credit per disabled dependent child at or under an age, while income is at most the limit. Where the state says so, the child credit is prorated by the state AGI (the base before deductions) over the federal AGI when the state AGI is lower. The federal tax that limits the nonrefundable part is the tax before credits when given; with only the tax after the nonrefundable credits, any tax left means the whole credit was allowed, and none left means the nonrefundable part is taken as zero. Where the state says so, the refundable part for three or more children is the larger of the earned-income route and the Social-Security-tax route.
Oklahoma's values · engine step (compute_state_tax_detail). Sources (Deductions, exemptions and credits): 2025 Oklahoma Resident Individual Income Tax Forms and Instructions (Form 511 Packet) (checked 2026-10-12); 2026 Oklahoma Income Tax Withholding Tables (Packet OW-2) (checked 2026-10-12); IRS Revenue Procedure 2025-32 (2026 inflation adjustments) (checked 2026-10-12); 2025 Form 511-EIC Oklahoma Earned Income Credit Worksheet (with 2020 EIC Table) (checked 2026-10-12); Rev. Proc. 2019-44 (2020 inflation adjustments), section 3.07 Earned Income Credit (checked 2026-10-12); 26 U.S.C. 32 (United States Code, 2020 edition) (checked 2026-10-12); 2025 Form 538-H Claim for Credit or Refund of Property Tax (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).
Oklahoma's values · engine step (state_tax_effective_config). Sources (Rate schedule): Enrolled House Bill No. 2764 (2025) (checked 2026-10-12); 2026 Oklahoma Income Tax Withholding Tables (Packet OW-2) (checked 2026-10-12); 2025 Form 511 Packet (Oklahoma resident income tax) (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.
Oklahoma's values · engine step (compute_state_tax_detail). Sources (Social Security): 2025 Oklahoma Resident Individual Income Tax Forms and Instructions (Form 511 Packet) (checked 2026-10-12)
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.
Oklahoma's values · engine step (compute_state_tax_detail). Sources (Capital gains): 2025 Oklahoma Resident Individual Income Tax Forms and Instructions (Form 511 Packet) (checked 2026-10-12); Form 511 Packet (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).
Oklahoma's values · engine step (compute_state_tax_detail). Sources (Social Security): 2025 Oklahoma Resident Individual Income Tax Forms and Instructions (Form 511 Packet) (checked 2026-10-12)
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).
Oklahoma's values · engine step (state_tax_refundable_credits). Sources (Deductions, exemptions and credits): 2025 Oklahoma Resident Individual Income Tax Forms and Instructions (Form 511 Packet) (checked 2026-10-12); 2026 Oklahoma Income Tax Withholding Tables (Packet OW-2) (checked 2026-10-12); IRS Revenue Procedure 2025-32 (2026 inflation adjustments) (checked 2026-10-12); 2025 Form 511-EIC Oklahoma Earned Income Credit Worksheet (with 2020 EIC Table) (checked 2026-10-12); Rev. Proc. 2019-44 (2020 inflation adjustments), section 3.07 Earned Income Credit (checked 2026-10-12); 26 U.S.C. 32 (United States Code, 2020 edition) (checked 2026-10-12); 2025 Form 538-H Claim for Credit or Refund of Property Tax (checked 2026-10-12)

Rate schedule

Single

Taxable income from	to	Rate
$0	$3,750	0%
$3,750	$4,900	2.5%
$4,900	$7,200	3.5%
$7,200	and up	4.5%

Married filing jointly

Taxable income from	to	Rate
$0	$7,500	0%
$7,500	$9,800	2.5%
$9,800	$14,400	3.5%
$14,400	and up	4.5%

Head of household

Taxable income from	to	Rate
$0	$7,500	0%
$7,500	$9,800	2.5%
$9,800	$14,400	3.5%
$14,400	and up	4.5%

Married filing separately: the engine computes the MFJ tax on twice the income and halves it, which is the same as halving every MFJ threshold and the MFJ deduction.

Enrolled House Bill No. 2764 (2025), Oklahoma Legislature. For tax year 2026 Oklahoma taxes single filers at 0% on the first $3,750, 2.5% on the next $1,150, 3.5% on the next $2,300 and 4.5% on the remainder; joint filers, surviving spouses and heads of household at 0% on the first $7,500, 2.5% on the next $2,300, 3.5% on the next $4,600 and 4.5% above. Checked 2026-10-12.
2026 Oklahoma Income Tax Withholding Tables (Packet OW-2), Oklahoma Tax Commission. The Tax Commission's 2026 withholding tables apply the new 2.5%/3.5%/4.5% rate structure. Checked 2026-10-12.
2025 Form 511 Packet (Oklahoma resident income tax), Oklahoma Tax Commission. The Oklahoma tax table has one column for married filing joint and head of household. Checked 2026-10-12.

Deductions, exemptions and credits

Standard deduction (or the exemption the engine carries in its place): $6,350 single, $12,700 married filing jointly, $9,350 head of household.
Personal exemption, subtracted in addition: $1,000 single, $2,000 MFJ.

2025 Oklahoma Resident Individual Income Tax Forms and Instructions (Form 511 Packet), Oklahoma Tax Commission. Oklahoma's standard deduction is $6,350 for single/MFS and $12,700 for joint filers ($9,350 head of household), plus $1,000 for each personal exemption claimed. Engine 1.7.0: Form 511: $1,000 per dependent; line 15: 5% of the federal child tax credit allowed ($2,200 per child under 17 for 2026, its refundable part included), nothing above $100,000 of federal AGI (nonrefundable). Engine 1.8.0: when Oklahoma AGI is less than federal AGI (a Social Security, retirement or military subtraction), the child credit is prorated by their ratio (Schedule 511-F, at most 100%). Earned income credit (engine 1.12.0, refundableCredits): 5% of the federal EIC as in effect for 2020. Sales tax relief credit (engine 1.12.0): 538-S, $40 per exemption within the household income limits. Property tax relief credit (engine 1.12.0): 538-H, 65 or older or disabled, household income at most $12,000, at most $200. Checked 2026-10-12.
2026 Oklahoma Income Tax Withholding Tables (Packet OW-2), Oklahoma Tax Commission. The $1,000 personal exemption is still in force for 2026. Checked 2026-10-12.
IRS Revenue Procedure 2025-32 (2026 inflation adjustments), Internal Revenue Service. Engine 1.7.0: Form 511: $1,000 per dependent; line 15: 5% of the federal child tax credit allowed ($2,200 per child under 17 for 2026, its refundable part included), nothing above $100,000 of federal AGI (nonrefundable). Checked 2026-10-12.
2025 Form 511-EIC Oklahoma Earned Income Credit Worksheet (with 2020 EIC Table), Oklahoma Tax Commission. Earned income credit (engine 1.12.0, refundableCredits): 5% of the federal EIC as in effect for 2020. Checked 2026-10-12.
Rev. Proc. 2019-44 (2020 inflation adjustments), section 3.07 Earned Income Credit, Internal Revenue Service. Earned income credit (engine 1.12.0, refundableCredits): 5% of the federal EIC as in effect for 2020. Checked 2026-10-12.
26 U.S.C. 32 (United States Code, 2020 edition), U.S. Government Publishing Office (govinfo). Earned income credit (engine 1.12.0, refundableCredits): 5% of the federal EIC as in effect for 2020. Checked 2026-10-12.
2025 Form 538-H Claim for Credit or Refund of Property Tax, Oklahoma Tax Commission. Property tax relief credit (engine 1.12.0): 538-H, 65 or older or disabled, household income at most $12,000, at most $200. Checked 2026-10-12.

Age 65+ subtractions and credits

An extra $1,000 exemption for each taxpayer 65 or older when federal adjusted gross income, leaving out Roth-conversion income, is at most $15,000 (single), $19,000 (head of household), $25,000 (MFJ) or $12,500 (married filing separately).

2025 Form 511 Packet (Oklahoma resident income tax), Oklahoma Tax Commission. One more $1,000 exemption for each taxpayer 65 or older when federal AGI (leaving out Roth-conversion income) is at most $15,000 single, $25,000 joint, $12,500 married filing separately or $19,000 head of household. Checked 2026-10-12.

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.

2025 Oklahoma Resident Individual Income Tax Forms and Instructions (Form 511 Packet), Oklahoma Tax Commission. Social Security benefits included in federal AGI are subtracted on Schedule 511-A line 2, so Social Security is fully exempt in Oklahoma. Checked 2026-10-12.

IRA, 401(k) and private pensions

Pension, annuity and IRA/401(k) distributions: up to $10,000 excluded per taxpayer ($20,000 on a joint return) at any age.
Joint returns: the cap is per taxpayer. With the spouse's age given (couples), each spouse's own dollars are tested against that spouse's own age and cap; without it one household age applies and the $20,000 joint cap covers pooled income.

2025 Oklahoma Resident Individual Income Tax Forms and Instructions (Form 511 Packet), Oklahoma Tax Commission. Each individual may exclude up to $10,000 of distributions from 401, 457, 403 plans and IRAs/SEPs (Schedule 511-A line 6), with no age test or income limit, reduced by any government-retirement exclusion claimed on line 5. Checked 2026-10-12.

Public pensions

A public pension earned in service not covered by Social Security (read as a federal civil-service annuity paid in lieu of Social Security) is excluded in full, per taxpayer, and does not use the general retirement exclusion. It applies only when the caller says the pension was not covered (pensionPublicSsCovered: false on the API); without that, the pension draws only the general exclusion.

Otherwise public pensions follow the rules for other retirement income above.

2025 Oklahoma Resident Individual Income Tax Forms and Instructions (Form 511 Packet), Oklahoma Tax Commission. Oklahoma government and federal civil service pensions draw the same per-person $10,000 exclusion (Schedule 511-A line 5), shared with the line 6 private-retirement exclusion; a CSRS annuity paid in lieu of Social Security is excluded in full (line 3); military retirement is 100% excludable. Checked 2026-10-12.

Military retirement pay

Military retirement pay is fully exempt, at any age.
Rules are applied per taxpayer at that person's own age when the spouse's age is given. API value: rules.militaryRetirement.treatment: "exempt".

511 Pkt, Oklahoma Tax Commission. Each individual may exclude 100% of military retirement benefits. Checked 2026-10-12.

Roth conversions

A conversion draws the retirement-income exclusion together with distributions at any age; the part above the cap is taxed as ordinary income.

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

No official page states in terms that a Roth conversion qualifies for the line 6 $10,000 exclusion; the engine's treatment is an inference from the statute's 'total distributions or withdrawals' definition (68 O.S. 2358) which could not be fetched.

2025 Oklahoma Resident Individual Income Tax Forms and Instructions (Form 511 Packet), Oklahoma Tax Commission. Oklahoma starts from federal AGI and taxes IRA conversions in the same year as the federal return; a conversion is a distribution from a Section 408 IRA, so the engine lets it draw the per-person $10,000 retirement exclusion. Checked 2026-10-12.

Capital gains

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

2025 Oklahoma Resident Individual Income Tax Forms and Instructions (Form 511 Packet), Oklahoma Tax Commission. Long-term gains in federal AGI are taxed as ordinary income; the only capital-gain deduction is for Oklahoma-situs property held two or more years (511-A line 12), which does not apply to ordinary brokerage gains. Checked 2026-10-12.
Form 511 Packet, Oklahoma Tax Commission. The state return starts from federal adjusted gross income (federal taxable income in CO, IA, ND), so the federal capital-loss deduction (up to $3,000, $1,500 married filing separately) and its carryover are in the state base (engine 1.9.0: cap_loss_limit). 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.

Blindness and disability

An extra exemption of $1,000 for each person who is blind (the filer, and the spouse on a joint return).
The API applies these through its blind, disabled, spouse.blind and spouse.disabled fields; absent means false.

2025 Form 511 packet, Oklahoma Tax Commission. One more $1,000 exemption for each legally blind taxpayer. Checked 2026-10-12.

Part-year and nonresident returns

Part-year resident (Form 511-NR): the tax a full-year resident would owe on all the year's income, times the state's income ratio.
Nonresident (Form 511-NR): 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, not rounded (the form states no rounding), at most 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	Oklahoma'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	the couple's choice: separate returns or a joint resident return (both taxed as full-year residents).
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.

2025 Oklahoma Individual Income Tax Forms and Instructions for Nonresidents and Part-Year Residents (Form 511-NR packet), Oklahoma Tax Commission. Part-year / nonresident return (engine 1.12.0, residency): Checked 2026-10-12.
2025 Form 511-NR Oklahoma Nonresident/Part-Year Income Tax Return Packet, Oklahoma Tax Commission. Married couples whose residency differs (engine 1.13.0): Checked 2026-10-06.

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	$1,929.50
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	$2,959
Single, 60: $60,000 other ordinary income and a $50,000 Roth conversion	$3,954.50
Married filing jointly, 66: $30,000 IRA, a $40,000 Roth conversion, $30,000 Social Security ($25,500 federally taxable)	$1,159
Single, 58: $36,000 military retirement pay and $30,000 wages	$804.50
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	$709

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: $1,929.50

Line	Amount
Income total used by the income tests	$82,000
Retirement income and conversions excluded (not in the base)	$10,000
+ Other ordinary income in the base	$10,000
+ Retirement income in the base	$40,000
+ Long-term gain in the base	$5,000
− Standard deduction	$6,350
− Personal exemption	$1,000
= State taxable income	$47,650
Tax from the rate schedule	$1,929.50
= Tax before credits	$1,929.50
= Tax	$1,929.50

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: $2,959

Line	Amount
Income total used by the income tests	$144,000
Retirement income and conversions excluded (not in the base)	$20,000
+ Other ordinary income in the base	$20,000
+ Retirement income in the base	$60,000
+ Long-term gain in the base	$10,000
− Standard deduction	$12,700
− Personal exemption	$2,000
= State taxable income	$75,300
Tax from the rate schedule	$2,959
= Tax before credits	$2,959
= Tax	$2,959

Single, 60: $60,000 other ordinary income and a $50,000 Roth conversion: $3,954.50

Line	Amount
Income total used by the income tests	$110,000
Retirement income and conversions excluded (not in the base)	$10,000
+ Other ordinary income in the base	$60,000
+ Retirement income in the base	$40,000
− Standard deduction	$6,350
− Personal exemption	$1,000
= State taxable income	$92,650
Tax from the rate schedule	$3,954.50
= Tax before credits	$3,954.50
= Tax	$3,954.50

Married filing jointly, 66: $30,000 IRA, a $40,000 Roth conversion, $30,000 Social Security ($25,500 federally taxable): $1,159

Line	Amount
Income total used by the income tests	$95,500
Retirement income and conversions excluded (not in the base)	$20,000
+ Retirement income in the base	$50,000
− Standard deduction	$12,700
− Personal exemption	$2,000
= State taxable income	$35,300
Tax from the rate schedule	$1,159
= Tax before credits	$1,159
= Tax	$1,159

Single, 58: $36,000 military retirement pay and $30,000 wages: $804.50

Line	Amount
Income total used by the income tests	$66,000
Military pay excluded (not in the base)	$36,000
+ Other ordinary income in the base	$30,000
− Standard deduction	$6,350
− Personal exemption	$1,000
= State taxable income	$22,650
Tax from the rate schedule	$804.50
= Tax before credits	$804.50
= Tax	$804.50

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: $709

Line	Amount
Income total used by the income tests	$85,500
Retirement income and conversions excluded (not in the base)	$20,000
+ Other ordinary income in the base	$10,000
+ Retirement income in the base	$30,000
− Standard deduction	$12,700
− Personal exemption	$2,000
= State taxable income	$25,300
Tax from the rate schedule	$709
= Tax before credits	$709
= Tax	$709

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 Oklahoma'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
`brackets_single` (the single rate schedule's thresholds), `brackets_mfj` (the mfj rate schedule's thresholds), `brackets_hoh` (the hoh rate schedule's thresholds)	Fixed in law: held at the rules-year amount in every later year.	For tax year 2026 and later, 68 O.S. 2355(D) (HB 2764, 2025) sets nominal brackets (0% to $3,750/$7,500, then 2.5%, 3.5%, 4.5%); there is no inflation indexing. Rates (not brackets) may fall 0.25 point per revenue certification (see enacted_changes_not_modelled). Enrolled House Bill No. 2764 (2025), amending 68 O.S. § 2355 (Oklahoma Legislature, legislation): Subsection D sets the 2026+ brackets. Quoted: "(a) 0% tax on first $3,750.00 or part thereof, (b) 2.5% tax on the next $1,150.00 or part thereof"; "(a) 0% tax on first $7,500.00 or part thereof, (b) 2.5% tax on the next $2,300.00 or part thereof". Checked 2026-10-12.
`std_deduction_single`, `std_deduction_mfj`, `std_deduction_hoh`	Fixed in law: held at the rules-year amount in every later year.	68 O.S. 2358 sets the Oklahoma standard deduction at $6,350 / $12,700 / $9,350 (since 2017), with no inflation adjustment in the section; the 2025 OTC instructions still apply those amounts. (Statute read from the Senate's Title 68 compilation through Laws 2019; oscn.net was unreachable.) Oklahoma Statutes Title 68 (compiled through Laws 2019), § 2358 (Oklahoma State Senate, statute): Standard deduction amounts; no indexing clause in the section. Quoted: "Six Thousand Three Hundred Fifty Dollars ($6,350.00) for single or married filing separately". Checked 2026-10-12. 2025 Oklahoma Resident Individual Income Tax Forms and Instructions (Form 511 packet) (Oklahoma Tax Commission, instructions): Current amounts. Quoted: "If your filing status is "single" or "married filing separate," your Oklahoma standard deduction is $6,350.". Checked 2026-10-12.
`personal_exemption_single`, `personal_exemption_mfj`, `dep_exemption`, `blind_exemption`, `senior_lowinc_exemption`, `senior_lowinc_agi_single`, `senior_lowinc_agi_mfj`, `senior_lowinc_agi_mfs`, `senior_lowinc_agi_hoh`	Fixed in law: held at the rules-year amount in every later year.	$1,000 personal/dependent exemptions, an additional $1,000 per blind person and per person 65+ when federal AGI does not exceed $25,000 joint / $12,500 MFS / $15,000 single / $19,000 HOH; nominal in 68 O.S. 2358, no inflation adjustment. Oklahoma Statutes Title 68 (compiled through Laws 2019), § 2358 (Oklahoma State Senate, statute): Exemption amounts and AGI limits. Quoted: "allow personal exemptions of One Thousand Dollars ($1,000.00) in lieu of the personal exemptions allowed by the Internal Revenue Code"; "There shall be allowed an additional exemption of One Thousand Dollars ($1,000.00) for each taxpayer or spouse who is blind"; "(1) Twenty-five Thousand Dollars ($25,000.00) if married and filing jointly; (2) Twelve Thousand Five Hundred Dollars ($12,500.00) if married and filing separately; (3) Fifteen Thousand Dollars ($15,000.00) if single; and (4) Nineteen Thousand Dollars ($19,000.00) if a qualifying head of household". Checked 2026-10-12.
`senior_lowinc_min_age`	Attained age: the same age in every year.	Fixed attained age: 65 or older at the close of the tax year. Oklahoma Statutes Title 68 (compiled through Laws 2019), § 2358 (Oklahoma State Senate, statute): Age wording. Quoted: "who is sixty-five (65) years of age or older at the close of the tax year". Checked 2026-10-12.
`retirement_income_exclusion_single`, `retirement_income_exclusion_mfj`	Fixed in law: held at the rules-year amount in every later year.	Retirement benefits exclusion up to $10,000 per individual 'for the 2006 tax year and all subsequent tax years'; nominal, no inflation adjustment. Oklahoma Statutes Title 68 (compiled through Laws 2019), § 2358 (Oklahoma State Senate, statute): States the amount. Quoted: "Ten Thousand Dollars ($10,000.00) for the 2006 tax year and all subsequent tax years". Checked 2026-10-12. 2025 Oklahoma Resident Individual Income Tax Forms and Instructions (Form 511 packet) (Oklahoma Tax Commission, instructions): Current amount. Quoted: "Each individual may exclude their retirement benefits up to $10,000, but not to exceed the amount included in the Federal AGI.". Checked 2026-10-12.
`dep_child_credit`	Tied to an indexed federal amount: 5% of the federal child tax credit per child, IRC 24(h)(2) $2,200 indexed under IRC 24(i)(2) by the IRC 1(f)(3) cost-of-living adjustment (chained CPI-U, Sept-Aug average); the increase rounded down to a multiple of $100.	The credit is 5% of the federal child tax credit (greater of that or 20% of the federal child care credit); the federal $2,200 per child is indexed after 2025 by the IRC 1(f)(3) COLA (2024 base), increases rounded down to $100. Engine value = 5% x $2,200 (2026). Oklahoma Statutes Title 68 (compiled through Laws 2019), § 2357 (Oklahoma State Senate, statute): Credit is 5% of the federal child tax credit. Quoted: "five percent (5%) of the child tax credit allowed under the Internal Revenue Code, whichever amount is greater". Checked 2026-10-12. 26 U.S.C. 24 (Child tax credit) (Legal Information Institute (Cornell) - U.S. Code, federal): IRC 24(i)(2)-(3) indexes the $2,200 credit after 2025, increases rounded down to $100. Quoted: "the $2,200 amount in subsection (h)(2) shall be increased by an amount equal to"; "such increase shall be rounded to the next lowest multiple of $100". Checked 2026-10-12.
`dep_child_credit_agi_limit`	Fixed in law: held at the rules-year amount in every later year.	No credit if federal AGI exceeds $100,000; nominal, no adjustment. Oklahoma Statutes Title 68 (compiled through Laws 2019), § 2357 (Oklahoma State Senate, statute): AGI limit. Quoted: "is in excess of One Hundred Thousand Dollars ($100,000.00)". Checked 2026-10-12.
`dep_child_credit_max_age`	Attained age: the same age in every year.	Follows the federal qualifying child for the child tax credit: under 17 at year end (engine: 16 or younger). Fixed age. 26 U.S.C. 24 (Child tax credit) (Legal Information Institute (Cornell) - U.S. Code, federal): IRC 24(c)(1): qualifying child has not attained age 17. Quoted: "who has not attained age 17". Checked 2026-10-12.
`ok-federal-actc-2500` (a table held in code)	Fixed in law: held at the rules-year amount in every later year.	The federal refundable-part earned income threshold is $2,500 under IRC 24(h)(6); not indexed. 26 U.S.C. 24 (Child tax credit) (Legal Information Institute (Cornell) - U.S. Code, federal): IRC 24(h)(6) sets the $2,500 threshold (no inflation clause applies to it). Quoted: "Subsection (d)(1)(B)(i) shall be applied by substituting "$2,500" for "$3,000"". Checked 2026-10-12.
`eic_max_credit`, `eic_phaseout_start`, `eic_phaseout_start_mfj`	Tied to an indexed federal amount: federal EIC amounts, IRC 32(b)(2) indexed under IRC 32(j) by the IRC 1(f)(3) cost-of-living adjustment (chained CPI-U, Sept-Aug average); the increase rounded to the nearest $10.	In the engine these fields hold the CURRENT federal EIC (copied from MD), used only for the federal Schedule 8812 alternative ACTC (three or more children) inside Oklahoma's 5%-of-federal-child-credit computation. They are federal amounts indexed under IRC 32(j) (earned-income and phase-out amounts rounded to the nearest $10). Oklahoma's own 5% EIC (frozen at 2020 federal rules) is not modelled by the engine; see notes. 26 U.S.C. 32 (Earned income credit) (Legal Information Institute (Cornell) - U.S. Code, federal): IRC 32(j) indexes the EIC earned-income and phase-out amounts (rounded to the nearest $10) and the disqualified-investment-income limit (rounded down to $50) by the IRC 1(f)(3) cost-of-living adjustment. Quoted: "each of the dollar amounts in subsections (b)(2) and (i)(1) shall be increased by an amount equal to"; "such dollar amount shall be rounded to the nearest multiple of $10"; "such amount shall be rounded to the next lowest multiple of $50". Checked 2026-10-12.
`eic_invest_limit`	Tied to an indexed federal amount: IRC 32(i)(1) disqualified investment income limit, indexed under IRC 32(j) 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.	Current federal IRC 32(i) investment-income limit (used for the federal ACTC alternative), indexed under IRC 32(j), rounded down to $50. 26 U.S.C. 32 (Earned income credit) (Legal Information Institute (Cornell) - U.S. Code, federal): IRC 32(j) indexes the EIC earned-income and phase-out amounts (rounded to the nearest $10) and the disqualified-investment-income limit (rounded down to $50) by the IRC 1(f)(3) cost-of-living adjustment. Quoted: "each of the dollar amounts in subsections (b)(2) and (i)(1) shall be increased by an amount equal to"; "such dollar amount shall be rounded to the nearest multiple of $10"; "such amount shall be rounded to the next lowest multiple of $50". Checked 2026-10-12.
`eic_nochild_max_age`, `eic_nochild_min_age`	Attained age: the same age in every year.	Federal EIC age test for a filer without a qualifying child: at least 25 and under 65; fixed ages. 26 U.S.C. 32 (Earned income credit) (Legal Information Institute (Cornell) - U.S. Code, federal): IRC 32(c)(1)(A)(ii)(II): a filer without a qualifying child must be at least 25 and not yet 65 at the close of the taxable year. Quoted: "has attained age 25 but not attained age 65 before the close of the taxable year". Checked 2026-10-12.
`cap_loss_limit`, `cap_loss_limit_mfs`	Fixed in law: held at the rules-year amount in every later year.	Oklahoma 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.
`ok-credits` (a table held in code)	Fixed in law: held at the rules-year amount in every later year.	68 O.S. 5011 (538-S), 5011 (538-H) and the EIC's tie to the 2020 federal credit are fixed amounts. 2025 Oklahoma Resident Individual Income Tax Forms and Instructions (511 packet incl. Form 538-S) (Oklahoma Tax Commission, agency_page): Sales Tax Relief Credit (Form 538-S, claimed on Form 511) Quoted: "You are 65 years of age or older by December 31, 2025; or"; "If any one of the above three items pertains to you, your total gross household income limit is increased to $50,000.". Checked 2026-10-12. 2025 Oklahoma 511 packet (Oklahoma Tax Commission, agency_page): Credit for Property Tax Relief (Form 538-H) Quoted: "not exceed $12,000, may file a claim for property tax relief on the amount of property taxes paid on the household they"; "The credit may not exceed $200. The claim must be made on Form 538-H.". Checked 2026-10-12. 2025 Form 538-H Claim for Credit or Refund of Property Tax (Oklahoma Tax Commission, agency_page): Credit for Property Tax Relief (Form 538-H) Quoted: "X 1% (0.01). Enter result here"; "Amount of credit or refund, subtract line 16 from line 15 (not to exceed $200)". Checked 2026-10-12. Rev. Proc. 2019-44 (2020 inflation adjustments), section 3.07 Earned Income Credit (Internal Revenue Service, agency_page): Oklahoma EIC = 5% of the federal EIC computed under the requirements in effect for tax year 2020: the 2020 federal parameters and OTC's 2020 EIC Table Quoted: "For taxable years beginning in 2020, the following amounts are used"; "Item One Two Three or More None". Checked 2026-10-12. 26 U.S.C. 32 (United States Code, 2020 edition) (U.S. Government Publishing Office (govinfo), statute): Oklahoma EIC = 5% of the federal EIC computed under the requirements in effect for tax year 2020: the 2020 federal parameters and OTC's 2020 EIC Table Quoted: "1 qualifying child 34 15.98"; "2 qualifying children 40 21.06". Checked 2026-10-12.

Enacted for later years, not applied by the projection

Starting with the State Board of Equalization's December 2026 / February 2027 certification, each certification that revenue growth exceeds the rate-reduction threshold cuts every 68 O.S. 2355(D) rate by 0.25 percentage point, effective the following January 1 (first possible 2028), until rates reach 0%; a declared revenue failure defers the cut. (2028+; conditional)
- Enrolled House Bill No. 2764 (2025), amending 68 O.S. § 2355 (Oklahoma Legislature, legislation): Subsection E revenue-triggered rate cuts. Quoted: "shall each be reduced by twenty-five one-hundredths (0.25) of a percentage point (0.0025) until the applicable rate equals zero percent (0%)". Checked 2026-10-12.

What the engine does not calculate, and known approximations

The child credit's nonrefundable federal part is limited by federalTaxBeforeCredits when given; with only federalTax (line 22) a positive figure means the whole federal credit was allowed, and 0 means the nonrefundable part is taken as 0 (the smaller credit) (engine 1.8.0).
The child care credit alternative (a share of the federal child and dependent care credit) needs expenses and is not calculated; the child tax credit share is. Sources: 2025 Oklahoma Resident Individual Income Tax Forms and Instructions (Form 511 Packet) (checked 2026-10-12); 2026 Oklahoma Income Tax Withholding Tables (Packet OW-2) (checked 2026-10-12); IRS Revenue Procedure 2025-32 (2026 inflation adjustments) (checked 2026-10-12); 2025 Form 511-EIC Oklahoma Earned Income Credit Worksheet (with 2020 EIC Table) (checked 2026-10-12); Rev. Proc. 2019-44 (2020 inflation adjustments), section 3.07 Earned Income Credit (checked 2026-10-12); 26 U.S.C. 32 (United States Code, 2020 edition) (checked 2026-10-12); 2025 Form 538-H Claim for Credit or Refund of Property Tax (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 Schedule 511-A line 6, including the per-person exclusion.

Golden scenarios (hand-computed expected tax, asserted to within $1): OKCONV1, OKSP1, OKSP2, OKSP3.
State-specific unit tests: test_conversion_on_cap_al_la_ok_sc, test_spouse_split_sentinels, test_ok_per_spouse_conversion, test_spouse_split_clamps, test_credit_programs_1, test_equal_ages_split_matches_legacy_split, test_ok_exemption_and_hoh, test_ok_low_income_senior_exemption, test_ok_csrs_in_lieu_of_ss.
Structural tests covering every state: 7.
State forms and worksheets followed in the test derivations: Form 511 Schedule 511-A line 6.