North Dakota state income tax: engine rules, 2026

How the tax is computed

Every step the engine takes for North Dakota, 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 North Dakota'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):

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.
   North Dakota's values · engine step (select_brackets). Sources (Rate schedule): 2025 North Dakota Individual Income Tax Booklet (Forms ND-1 and ND-EZ instructions) (checked 2026-10-12); Form ND-1ES Estimated Income Tax - Individuals (2026), 2026 Forms ND-1 and ND-EZ Tax Rate Schedules (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).
   North Dakota's values · engine step (select_brackets). Sources (Rate schedule): 2025 North Dakota Individual Income Tax Booklet (Forms ND-1 and ND-EZ instructions) (checked 2026-10-12); Form ND-1ES Estimated Income Tax - Individuals (2026), 2026 Forms ND-1 and ND-EZ Tax Rate Schedules (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.
   North Dakota's values · engine step (select_brackets). Sources (Rate schedule): 2025 North Dakota Individual Income Tax Booklet (Forms ND-1 and ND-EZ instructions) (checked 2026-10-12); Form ND-1ES Estimated Income Tax - Individuals (2026), 2026 Forms ND-1 and ND-EZ Tax Rate Schedules (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. 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.
9. 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.
   North Dakota's values · engine step (compute_state_tax_detail). Sources (Military retirement pay): Military service members (checked 2026-10-12)
10. 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.
    North Dakota's values · engine step (military_exempt_one). Sources (Military retirement pay): Military service members (checked 2026-10-12)
11. 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).
    North Dakota's values · engine step (compute_state_tax_detail). Sources (Capital gains): 2025 North Dakota Individual Income Tax Booklet (Forms ND-1 and ND-EZ instructions) (checked 2026-10-12); 2025 North Dakota Individual Income Tax Booklet (checked 2026-10-12); 2025 Schedule D (Form 1040), Capital Gains and Losses (checked 2026-10-12)
12. Social Security exempt None of the federally taxable benefit enters the base.
    North Dakota's values · engine step (ss_amount_in_state_base). Sources (Social Security): 2025 North Dakota Individual Income Tax Booklet (Forms ND-1 and ND-EZ instructions) (checked 2026-10-12)
13. 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.
    North Dakota's values · engine step (compute_state_tax_detail). Sources (IRA, 401(k) and private pensions): 2025 North Dakota Individual Income Tax Booklet (Forms ND-1 and ND-EZ instructions) (checked 2026-10-12)
14. 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.
    North Dakota's values · engine step (compute_state_tax_detail). Sources (Roth conversions): 2025 North Dakota Individual Income Tax Booklet (Forms ND-1 and ND-EZ instructions) (checked 2026-10-12)
15. 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.
    North Dakota's values · engine step (compute_state_tax_detail). Sources (Capital gains): 2025 North Dakota Individual Income Tax Booklet (Forms ND-1 and ND-EZ instructions) (checked 2026-10-12); 2025 North Dakota Individual Income Tax Booklet (checked 2026-10-12); 2025 Schedule D (Form 1040), Capital Gains and Losses (checked 2026-10-12)
16. 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.
    North Dakota's values · engine step (compute_state_tax_detail). Sources (Deductions, exemptions and credits): 2025 North Dakota Individual Income Tax Booklet (Forms ND-1 and ND-EZ instructions) (checked 2026-10-12); IRS releases tax inflation adjustments for tax year 2026, including amendments from the One, Big, Beautiful Bill (checked 2026-10-12); 28709 form nd 1es 2026 (checked 2026-10-12); N.D.C.C. 57-38-01.28 (marriage penalty credit) (checked 2026-10-12); 2025 Individual Income Tax Booklet (Marriage Penalty Credit Worksheet) (checked 2026-10-12)
17. 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.
    North Dakota's values · engine step (compute_state_tax_detail). Sources (Blindness and disability): Rev. Proc. 2025-32 (2026 inflation adjustments) (checked 2026-10-12)
18. Federal senior deduction taken against the state base For each taxpayer 65 or older: the amount, reduced by the rate times the income total above the status's start (joint start on a joint return); none for married filing separately. In the states whose base is federal taxable income it is taken only when the caller does not supply that figure (it is already in it).
    North Dakota's values · engine step (compute_state_tax_detail). Sources (Age 65+ subtractions and credits): Rev. Proc. 2025-32 (2026 inflation adjustments) (checked 2026-10-12); Schedule 1-A (Form 1040), Additional Deductions (checked 2026-10-12); 2025 North Dakota individual income tax booklet (checked 2026-10-12)
19. 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.
20. Starting from federal taxable income only when the caller supplies federal taxable income (the planner; not the API) When the caller supplies federal taxable income (the planner does; the API does not), the base starts from it, adds the gains in it (less the state's gain subtraction), and subtracts the state's own exclusions and subtractions; the state's deduction is not subtracted again.
    North Dakota's values · engine step (compute_state_tax_detail). Sources (Interaction with the federal return): 2025 North Dakota Individual Income Tax Booklet (Forms ND-1 and ND-EZ instructions) (checked 2026-10-12)
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.
    North Dakota's values · engine step (compute_state_tax_detail). Sources (Rate schedule): 2025 North Dakota Individual Income Tax Booklet (Forms ND-1 and ND-EZ instructions) (checked 2026-10-12); Form ND-1ES Estimated Income Tax - Individuals (2026), 2026 Forms ND-1 and ND-EZ Tax Rate Schedules (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.
    North Dakota's values · engine step (apply_state_brackets). Sources (Rate schedule): 2025 North Dakota Individual Income Tax Booklet (Forms ND-1 and ND-EZ instructions) (checked 2026-10-12); Form ND-1ES Estimated Income Tax - Individuals (2026), 2026 Forms ND-1 and ND-EZ Tax Rate Schedules (checked 2026-10-12)
24. Marriage credit joint returns with each spouse's own amounts given On a joint return with each spouse's own amounts: the tax on joint taxable income on the joint schedule less the single-schedule tax on the lesser-earning spouse's income minus the state's amount (half the joint standard deduction) and on the rest of joint taxable income; at most the cap where there is one; none when that is zero or less. Each spouse's income counts to the extent it is in the state base: own wages, own share of the retirement income left in the base (own distributions less own excluded military pay), of the conversion and of the Social Security in the base (by the gross split, else half).
    North Dakota's values · engine step (compute_state_tax_detail). Sources (Deductions, exemptions and credits): 2025 North Dakota Individual Income Tax Booklet (Forms ND-1 and ND-EZ instructions) (checked 2026-10-12); IRS releases tax inflation adjustments for tax year 2026, including amendments from the One, Big, Beautiful Bill (checked 2026-10-12); 28709 form nd 1es 2026 (checked 2026-10-12); N.D.C.C. 57-38-01.28 (marriage penalty credit) (checked 2026-10-12); 2025 Individual Income Tax Booklet (Marriage Penalty Credit Worksheet) (checked 2026-10-12)
25. 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.
26. 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).
    North Dakota's values · engine step (state_tax_effective_config). Sources (Rate schedule): 2025 North Dakota Individual Income Tax Booklet (Forms ND-1 and ND-EZ instructions) (checked 2026-10-12); Form ND-1ES Estimated Income Tax - Individuals (2026), 2026 Forms ND-1 and ND-EZ Tax Rate Schedules (checked 2026-10-12)
27. 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.
    North Dakota's values · engine step (compute_state_tax_detail). Sources (Social Security): 2025 North Dakota Individual Income Tax Booklet (Forms ND-1 and ND-EZ instructions) (checked 2026-10-12)
28. The capital-loss deduction the state allows With a net capital loss (capitalLoss): the smaller of the loss and the state's limit (the federal $3,000 / $1,500 where the state follows the federal return; MA $2,000, and no more than the interest and dividends); AL the loss less the part carried in, unlimited; PA and NJ none. It comes off the income total the income tests use (and the Social Security worksheets' income); the gross-income filing test (LA) reads the total before it. Engine 1.13.1: with a rental loss (rentalNetIncome below 0, the federal Schedule E line 26 amount) the state allows, the whole loss where the state starts from federal AGI or follows the federal schedule, none in PA and NJ (rental_loss_no_offset): it comes off the same income the same way; a rental profit is other ordinary income.
    North Dakota's values · engine step (compute_state_tax_detail). Sources (Capital gains): 2025 North Dakota Individual Income Tax Booklet (Forms ND-1 and ND-EZ instructions) (checked 2026-10-12); 2025 North Dakota Individual Income Tax Booklet (checked 2026-10-12); 2025 Schedule D (Form 1040), Capital Gains and Losses (checked 2026-10-12)
29. 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).
    North Dakota's values · engine step (compute_state_tax_detail). Sources (Social Security): 2025 North Dakota Individual Income Tax Booklet (Forms ND-1 and ND-EZ instructions) (checked 2026-10-12)
30. Qualified dividend exclusion only when the caller gives qualified dividends The share of the qualified dividends (qualifiedDividends, part of the other ordinary income, never more than it less the wages) that the state excludes leaves the other ordinary income.
    North Dakota's values · engine step (compute_state_tax_detail). Sources (Capital gains): 2025 North Dakota Individual Income Tax Booklet (Forms ND-1 and ND-EZ instructions) (checked 2026-10-12); 2025 North Dakota Individual Income Tax Booklet (checked 2026-10-12); 2025 Schedule D (Form 1040), Capital Gains and Losses (checked 2026-10-12)
31. 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).
    North Dakota's values · engine step (state_tax_refundable_credits). Sources (Deductions, exemptions and credits): 2025 North Dakota Individual Income Tax Booklet (Forms ND-1 and ND-EZ instructions) (checked 2026-10-12); IRS releases tax inflation adjustments for tax year 2026, including amendments from the One, Big, Beautiful Bill (checked 2026-10-12); 28709 form nd 1es 2026 (checked 2026-10-12); N.D.C.C. 57-38-01.28 (marriage penalty credit) (checked 2026-10-12); 2025 Individual Income Tax Booklet (Marriage Penalty Credit Worksheet) (checked 2026-10-12)

Worked examples

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

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.

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 North Dakota's law moves it. Rates and the rules themselves stay the 2026 ones (how projection works).

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

• The licensed peace officer retirement exclusion (ND-1 line 9) is not modeled. (Public pensions)
• Federal deductions the inputs do not carry are not subtracted: North Dakota starts from federal taxable income, so itemized deductions and the federal Schedule 1-A deductions for tips, overtime and car-loan interest would lower it; only the standard deduction, the age and blindness amounts and the senior deduction are taken. Sources: 2025 North Dakota Individual Income Tax Booklet (Forms ND-1 and ND-EZ instructions) (checked 2026-10-12).
• The marriage penalty credit (Form ND-1 line 22) needs each spouse's own amounts: without a spouse object it is not calculated. With them the engine counts each spouse's income to the extent it is in North Dakota taxable income (the worksheet's instructions list the federally taxable Social Security, which North Dakota excludes) and caps the credit at the TY2025 maximum, $312 (the indexed 2026 maximum is not published). Self-employment income is not an input: only wages count as earned income for the credit. Sources: 2025 North Dakota Individual Income Tax Booklet (Forms ND-1 and ND-EZ instructions) (checked 2026-10-12); IRS releases tax inflation adjustments for tax year 2026, including amendments from the One, Big, Beautiful Bill (checked 2026-10-12); 28709 form nd 1es 2026 (checked 2026-10-12); N.D.C.C. 57-38-01.28 (marriage penalty credit) (checked 2026-10-12); 2025 Individual Income Tax Booklet (Marriage Penalty Credit Worksheet) (checked 2026-10-12).
• The other Schedule ND-1TC credits (the family member care credit and the long-term care partnership insurance credit, and the business and program credits) are not calculated: they need expenses, premiums or certificates the inputs do not carry. Sources: 2025 North Dakota Individual Income Tax Booklet (Forms ND-1 and ND-EZ instructions) (checked 2026-10-12); IRS releases tax inflation adjustments for tax year 2026, including amendments from the One, Big, Beautiful Bill (checked 2026-10-12); 28709 form nd 1es 2026 (checked 2026-10-12); N.D.C.C. 57-38-01.28 (marriage penalty credit) (checked 2026-10-12); 2025 Individual Income Tax Booklet (Marriage Penalty Credit Worksheet) (checked 2026-10-12).
• North Dakota adjustments for income the inputs do not separate are not calculated: interest from U.S. obligations, the licensed peace officer retirement exclusion, the College SAVE deduction and the organ donor deduction. Sources: 2025 North Dakota Individual Income Tax Booklet (Forms ND-1 and ND-EZ instructions) (checked 2026-10-12); IRS releases tax inflation adjustments for tax year 2026, including amendments from the One, Big, Beautiful Bill (checked 2026-10-12); 28709 form nd 1es 2026 (checked 2026-10-12); N.D.C.C. 57-38-01.28 (marriage penalty credit) (checked 2026-10-12); 2025 Individual Income Tax Booklet (Marriage Penalty Credit Worksheet) (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 Engine 1.2.0 tests follow the 2026 ND-1ES rate schedules for single, joint and head of household.

• Golden scenarios (hand-computed expected tax, asserted to within $1): NDCONF1.
• State-specific unit tests: test_group2_ltcg_partial_exclusion, test_nd_hoh_own_schedule, test_d12_conformity_states, test_c_interface_edges, test_engine_180_s3, test_nd_2026_thresholds, test_conformity_component_path.
• Structural tests covering every state: 8.
• State forms and worksheets followed in the test derivations: ND-1ES (2026) rate schedules.