State tax docs / States / South Carolina

South Carolina state income tax: engine rules, 2026

How the QuantCalc engine computes South Carolina 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 SC).

How the tax is computed

Every step the engine takes for South Carolina, 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 South Carolina'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	single schedule	single schedule
Top rate	5.21% from $30,000	5.21% from $30,000	5.21% from $30,000	5.21% from $30,000
Standard deduction, under 65	$15,000	$30,000	$15,000	$22,500
Standard deduction at 70 (joint: both 70)	$15,000	$30,000	$15,000	$22,500
Personal exemption	none	none	none	none
Age subtractions at 70 (joint: both 70)	$15,000	$30,000	$15,000	$15,000

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.
South Carolina's values · engine step (select_brackets). Sources (Rate schedule): H.4216 (Act No. 110 of 2026), ratified text (checked 2026-10-12); SC Information Letter #26-20 (individual income tax changes under H.4216 / Act 110) (checked 2026-10-12); Information Letter #26-20 (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).
South Carolina's values · engine step (select_brackets). Sources (Rate schedule): H.4216 (Act No. 110 of 2026), ratified text (checked 2026-10-12); SC Information Letter #26-20 (individual income tax changes under H.4216 / Act 110) (checked 2026-10-12); Information Letter #26-20 (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.
South Carolina's values · engine step (select_brackets). Sources (Rate schedule): H.4216 (Act No. 110 of 2026), ratified text (checked 2026-10-12); SC Information Letter #26-20 (individual income tax changes under H.4216 / Act 110) (checked 2026-10-12); Information Letter #26-20 (checked 2026-10-12)
The income total every income test uses Other ordinary income + retirement distributions (before any exclusion) + conversion + federally taxable Social Security + long-term gains + Railroad Retirement Tier 2. It stands in for federal adjusted gross income in every threshold, cliff and phase-out below; state subtractions do not reduce it.
engine step (compute_state_tax_detail). Engine convention, no external source: The inputs are the federal AGI components, so their sum is federal AGI for these income types.
Attributing income to each spouse joint returns with each spouse's own amounts given With a caller's split (the API's spouse object), each spouse's own distributions (employer-plan money included), pension, public pension, conversion, wages and military pay; spouse 2's shares are clamped into the household totals and spouse 1 gets the rest. Without a split, in per-person mode, every item is divided 50/50. Social Security is divided by each spouse's own gross benefits where the caller gives spouse.socialSecurityGross, else 50/50; other ordinary income and gains are always divided 50/50 where a rule needs a per-person amount. The split is used only where a state's rule is per taxpayer; household totals stay authoritative for the base and the income tests.
engine step (compute_state_tax_detail). Engine convention, no external source: Equal attribution is the neutral split when the owner of a dollar is not known.
Early IRA distributions The IRA and employer-plan dollars each person took before 59½: the amount the caller gave, else every such dollar of a person under 59 at the end of the year (none of an older person, or when the age is not given). Where the state keeps its retirement break only for some federal early-withdrawal exceptions, the other early dollars leave the retirement pool and are taxed as ordinary income; the exception is the caller's, else death for a survivor's benefits, disability for a disabled person, else none. Where the state taxes only the part over the IRA basis, the part within it is left out altogether. A kept exception passes the state's IRA age gate. The additional state tax on the early dollars with no exception is added before the credits, or after them where the state says so (next steps).
South Carolina's values · engine step (compute_state_tax_detail). Sources (IRA, 401(k) and private pensions): S.C. Code of Laws Title 12, Chapter 6 (South Carolina Income Tax Act) (checked 2026-10-12); SC Revenue Ruling #22-11 (Section 12-6-1170 and 12-6-1171 deductions) (checked 2026-10-12); South Carolina Department of Revenue: SC1040Instr_2025.pdf (checked 2026-10-12)
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.
South Carolina's values · engine step (compute_state_tax_detail). Sources (Blindness and disability): South Carolina Department of Revenue: SC1040Instr_2025.pdf (checked 2026-10-12); South Carolina Legislature: t12c006.php (checked 2026-10-12); South Carolina Department of Revenue: RR22-11.pdf (checked 2026-10-12)
Survivor benefits 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's retirement income (the caller's survivorBenefits: the person's pension and IRA income is received as a beneficiary; without a spouse object the fact describes the household). Where the state deducts survivor benefits, the pension part leaves the base before Ohio-style income tests (the IRA part stays: an inherited account was payable without the death). Where the state gives a surviving spouse its own deduction, up to the state's amount of that income is deducted and the rest gets no own-plan retirement deduction (it is not the survivor's own plan) and is taxed as ordinary income; military pay keeps the military rule. The surviving-spouse deduction is the higher amount when the deceased spouse would have reached the state's age (the deceased spouse's age, when given).
South Carolina's values · engine step (compute_state_tax_detail). Sources (IRA, 401(k) and private pensions): S.C. Code of Laws Title 12, Chapter 6 (South Carolina Income Tax Act) (checked 2026-10-12); SC Revenue Ruling #22-11 (Section 12-6-1170 and 12-6-1171 deductions) (checked 2026-10-12); South Carolina Department of Revenue: SC1040Instr_2025.pdf (checked 2026-10-12)
Keeping the per-spouse shares inside the household joint returns with each spouse's own amounts given After the public-pension and employer-pension carve-outs, if the two spouses' remaining shares add up to more than the household's exclusion-eligible distributions (an inconsistent split), spouse 1's share is reduced so they do not.
engine step (compute_state_tax_detail). Engine convention, no external source: Input normalisation.
Military retirement pay The state's military rule runs first, on military pay alone, per taxpayer: each spouse's own pay at their own age when attributed, otherwise half each at the household age on a joint return. Exempt dollars leave the base; the rest become pension dollars for the general retirement rules. Where the state lets a disabled retiree qualify at any age, a disabled person is treated as having reached the rule's age.
South Carolina's values · engine step (compute_state_tax_detail). Sources (Military retirement pay): T12c006 (checked 2026-10-12); 2025 SC1040 instructions (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.
South Carolina's values · engine step (military_exempt_one). Sources (Military retirement pay): T12c006 (checked 2026-10-12); 2025 SC1040 instructions (checked 2026-10-12)
Military exclusion reduces other caps Where the statute says so, the military amount a taxpayer excluded reduces that taxpayer's general retirement-exclusion cap, their age-65 subtraction, or both. A survivor's military pay (a surviving-spouse military deduction) reduces neither, where the state says so.
South Carolina's values · engine step (compute_state_tax_detail). Sources (Military retirement pay): T12c006 (checked 2026-10-12); 2025 SC1040 instructions (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).
South Carolina's values · engine step (compute_state_tax_detail). Sources (Capital gains): S.C. Code of Laws Title 12, Chapter 6 (South Carolina Income Tax Act) (checked 2026-10-12); Individual Income Tax FAQs (checked 2026-10-12); Information Letter #26-20 (2026 individual income tax changes) (checked 2026-10-12); 2025 Schedule D (Form 1040), Capital Gains and Losses (checked 2026-10-12)
Social Security exempt None of the federally taxable benefit enters the base.
South Carolina's values · engine step (ss_amount_in_state_base). Sources (Social Security): S.C. Code of Laws Title 12, Chapter 6 (South Carolina Income Tax Act) (checked 2026-10-12); SC Revenue Ruling #22-11 (Section 12-6-1170 and 12-6-1171 deductions) (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.
South Carolina's values · engine step (compute_state_tax_detail). Sources (Roth conversions): SC Information Letter #26-20 (individual income tax changes under H.4216 / Act 110) (checked 2026-10-12); SC Revenue Ruling #22-11 (Section 12-6-1170 and 12-6-1171 deductions) (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.
South Carolina's values · engine step (compute_state_tax_detail). Sources (IRA, 401(k) and private pensions): S.C. Code of Laws Title 12, Chapter 6 (South Carolina Income Tax Act) (checked 2026-10-12); SC Revenue Ruling #22-11 (Section 12-6-1170 and 12-6-1171 deductions) (checked 2026-10-12); South Carolina Department of Revenue: SC1040Instr_2025.pdf (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.
South Carolina's values · engine step (compute_state_tax_detail). Sources (Roth conversions): SC Information Letter #26-20 (individual income tax changes under H.4216 / Act 110) (checked 2026-10-12); SC Revenue Ruling #22-11 (Section 12-6-1170 and 12-6-1171 deductions) (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.
South Carolina's values · engine step (compute_state_tax_detail). Sources (IRA, 401(k) and private pensions): S.C. Code of Laws Title 12, Chapter 6 (South Carolina Income Tax Act) (checked 2026-10-12); SC Revenue Ruling #22-11 (Section 12-6-1170 and 12-6-1171 deductions) (checked 2026-10-12); South Carolina Department of Revenue: SC1040Instr_2025.pdf (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.
South Carolina's values · engine step (compute_state_tax_detail). Sources (IRA, 401(k) and private pensions): S.C. Code of Laws Title 12, Chapter 6 (South Carolina Income Tax Act) (checked 2026-10-12); SC Revenue Ruling #22-11 (Section 12-6-1170 and 12-6-1171 deductions) (checked 2026-10-12); South Carolina Department of Revenue: SC1040Instr_2025.pdf (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.
South Carolina's values · engine step (compute_state_tax_detail). Sources (Roth conversions): SC Information Letter #26-20 (individual income tax changes under H.4216 / Act 110) (checked 2026-10-12); SC Revenue Ruling #22-11 (Section 12-6-1170 and 12-6-1171 deductions) (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.
South Carolina's values · engine step (retirement_distributions_in_state_base). Sources (IRA, 401(k) and private pensions): S.C. Code of Laws Title 12, Chapter 6 (South Carolina Income Tax Act) (checked 2026-10-12); SC Revenue Ruling #22-11 (Section 12-6-1170 and 12-6-1171 deductions) (checked 2026-10-12); South Carolina Department of Revenue: SC1040Instr_2025.pdf (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.
South Carolina's values · engine step (retirement_distributions_in_state_base). Sources (IRA, 401(k) and private pensions): S.C. Code of Laws Title 12, Chapter 6 (South Carolina Income Tax Act) (checked 2026-10-12); SC Revenue Ruling #22-11 (Section 12-6-1170 and 12-6-1171 deductions) (checked 2026-10-12); South Carolina Department of Revenue: SC1040Instr_2025.pdf (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.
South Carolina's values · engine step (per_taxpayer_cap_single). Sources (IRA, 401(k) and private pensions): S.C. Code of Laws Title 12, Chapter 6 (South Carolina Income Tax Act) (checked 2026-10-12); SC Revenue Ruling #22-11 (Section 12-6-1170 and 12-6-1171 deductions) (checked 2026-10-12); South Carolina Department of Revenue: SC1040Instr_2025.pdf (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.
South Carolina's values · engine step (compute_state_tax_detail). Sources (Capital gains): S.C. Code of Laws Title 12, Chapter 6 (South Carolina Income Tax Act) (checked 2026-10-12); Individual Income Tax FAQs (checked 2026-10-12); Information Letter #26-20 (2026 individual income tax changes) (checked 2026-10-12); 2025 Schedule D (Form 1040), Capital Gains and Losses (checked 2026-10-12)
Standard deduction phase-out Above the start the deduction is scaled by 1 − (income − start) / width, down to zero, with head-of-household and separate starts where the state has them; where the state says so a head of household never gets less than the single deduction at the same income. Where the state rounds the reduction, it is rounded down to that multiple before it is taken. Where the state says so the income is its own (the base after its subtractions) rather than the income total.
South Carolina's values · engine step (compute_state_tax_detail). Sources (Deductions, exemptions and credits): SC Information Letter #26-20 (individual income tax changes under H.4216 / Act 110) (checked 2026-10-12); H.4216 (Act No. 110 of 2026), ratified text (checked 2026-10-12); Information Letter #26-20 (checked 2026-10-12); South Carolina Department of Revenue: SC1040Instr_2025.pdf (checked 2026-10-12); South Carolina Legislature: t12c006.php (checked 2026-10-12); South Carolina Department of Revenue: RR22-11.pdf (checked 2026-10-12); 2025 SC1040TC Tax Credits (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).
South Carolina's values · engine step (compute_state_tax_detail). Sources (Deductions, exemptions and credits): SC Information Letter #26-20 (individual income tax changes under H.4216 / Act 110) (checked 2026-10-12); H.4216 (Act No. 110 of 2026), ratified text (checked 2026-10-12); Information Letter #26-20 (checked 2026-10-12); South Carolina Department of Revenue: SC1040Instr_2025.pdf (checked 2026-10-12); South Carolina Legislature: t12c006.php (checked 2026-10-12); South Carolina Department of Revenue: RR22-11.pdf (checked 2026-10-12); 2025 SC1040TC Tax Credits (checked 2026-10-12)
Age subtraction At or above the age: the single amount, or the joint amount on a joint return (both spouses at the household age). In per-person mode, half the joint amount (or the single amount) per qualifying spouse. Plus the low-income amount below the income test; less the military exclusion where the statute says so; limited to the spouse's own income where the statute says so. Where the statute counts income from any source, the taxable remainder of the spouse's own public pension is part of that own income. Where the state says so, the Social Security that offsets a person's amount is that person's own.
South Carolina's values · engine step (compute_state_tax_detail). Sources (Age 65+ subtractions and credits): S.C. Code of Laws Title 12, Chapter 6 (South Carolina Income Tax Act) (checked 2026-10-12); SC Revenue Ruling #22-11 (Section 12-6-1170 and 12-6-1171 deductions) (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.
South Carolina's values · engine step (compute_state_tax_detail). Sources (Rate schedule): H.4216 (Act No. 110 of 2026), ratified text (checked 2026-10-12); SC Information Letter #26-20 (individual income tax changes under H.4216 / Act 110) (checked 2026-10-12); Information Letter #26-20 (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.
South Carolina's values · engine step (apply_state_brackets). Sources (Rate schedule): H.4216 (Act No. 110 of 2026), ratified text (checked 2026-10-12); SC Information Letter #26-20 (individual income tax changes under H.4216 / Act 110) (checked 2026-10-12); Information Letter #26-20 (checked 2026-10-12)
Two wage earner credit joint returns with each spouse's own amounts given Joint returns with each spouse's own amounts only, both spouses with wages: the rate times the lower earner's wages, counting at most the maximum.
engine step (compute_state_tax_detail). Sources: S.C. Code § 12-6-3330 (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).
South Carolina's values · engine step (state_tax_effective_config). Sources (Rate schedule): H.4216 (Act No. 110 of 2026), ratified text (checked 2026-10-12); SC Information Letter #26-20 (individual income tax changes under H.4216 / Act 110) (checked 2026-10-12); Information Letter #26-20 (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.
South Carolina's values · engine step (compute_state_tax_detail). Sources (Social Security): S.C. Code of Laws Title 12, Chapter 6 (South Carolina Income Tax Act) (checked 2026-10-12); SC Revenue Ruling #22-11 (Section 12-6-1170 and 12-6-1171 deductions) (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.
South Carolina's values · engine step (compute_state_tax_detail). Sources (Capital gains): S.C. Code of Laws Title 12, Chapter 6 (South Carolina Income Tax Act) (checked 2026-10-12); Individual Income Tax FAQs (checked 2026-10-12); Information Letter #26-20 (2026 individual income tax changes) (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).
South Carolina's values · engine step (compute_state_tax_detail). Sources (Social Security): S.C. Code of Laws Title 12, Chapter 6 (South Carolina Income Tax Act) (checked 2026-10-12); SC Revenue Ruling #22-11 (Section 12-6-1170 and 12-6-1171 deductions) (checked 2026-10-12)
Nonrefundable earned income credits SC, UT, DE and VA: a share of the federal EIC, nonrefundable, with the other credits (SC at most $200; DE, or its refundable share, the larger; VA, the larger of it and the credit for low-income individuals ($300 per exemption at a family income within the poverty guideline), or the refundable share, the larger).
South Carolina's values · engine step (st_compute). Sources (Deductions, exemptions and credits): SC Information Letter #26-20 (individual income tax changes under H.4216 / Act 110) (checked 2026-10-12); H.4216 (Act No. 110 of 2026), ratified text (checked 2026-10-12); Information Letter #26-20 (checked 2026-10-12); South Carolina Department of Revenue: SC1040Instr_2025.pdf (checked 2026-10-12); South Carolina Legislature: t12c006.php (checked 2026-10-12); South Carolina Department of Revenue: RR22-11.pdf (checked 2026-10-12); 2025 SC1040TC Tax Credits (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).
South Carolina's values · engine step (state_tax_refundable_credits). Sources (Deductions, exemptions and credits): SC Information Letter #26-20 (individual income tax changes under H.4216 / Act 110) (checked 2026-10-12); H.4216 (Act No. 110 of 2026), ratified text (checked 2026-10-12); Information Letter #26-20 (checked 2026-10-12); South Carolina Department of Revenue: SC1040Instr_2025.pdf (checked 2026-10-12); South Carolina Legislature: t12c006.php (checked 2026-10-12); South Carolina Department of Revenue: RR22-11.pdf (checked 2026-10-12); 2025 SC1040TC Tax Credits (checked 2026-10-12)

Rate schedule

Single

Taxable income from	to	Rate
$0	$30,000	1.99%
$30,000	and up	5.21%

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.

H.4216 (Act No. 110 of 2026), ratified text, South Carolina General Assembly. From tax year 2026 South Carolina taxes income under $30,000 at 1.99% and income of $30,000 or more at 5.21% minus $966, one schedule for all filing statuses (Act 110 of 2026). Checked 2026-10-12.
SC Information Letter #26-20 (individual income tax changes under H.4216 / Act 110), South Carolina Department of Revenue. The Department's 2026 tax computation: 1.99% of taxable income below $30,000; 5.21% of taxable income minus $966 at $30,000 or more. Checked 2026-10-12.
Information Letter #26-20, South Carolina Department of Revenue. One schedule for every individual (married filing separately included): 1.99% to $30,000, 5.21% above. Checked 2026-10-12.

Deductions, exemptions and credits

Standard deduction (or the exemption the engine carries in its place): $15,000 single, $30,000 married filing jointly, $22,500 head of household.
The standard deduction phases out ratably as income rises above $40,000 (single) and $80,000 (MFJ), reaching zero $55,000 and $110,000 above those points; head of household from $60,000 over $82,500.
The phase-out's reduction is rounded down to a multiple of $10 before it is taken.

SC Information Letter #26-20 (individual income tax changes under H.4216 / Act 110), South Carolina Department of Revenue. For 2026 South Carolina replaces the federal standard/itemized deduction with the SC Income Adjusted Deduction (SCIAD): $15,000 single/MFS reduced by (AGI - $40,000)/$55,000, $30,000 joint reduced by (AGI - $80,000)/$110,000, and $22,500 head of household reduced by (AGI - $60,000)/$82,500. Earned income credit (engine 1.12.0): 125% of the federal EIC, nonrefundable, at most $200 from 2026. Checked 2026-10-12.
H.4216 (Act No. 110 of 2026), ratified text, South Carolina General Assembly. Act 110 adds Section 12-6-1140(15), the SCIAD and its federal-AGI phase-out fractions. Checked 2026-10-12.
Information Letter #26-20, South Carolina Department of Revenue. The SCIAD reduction is rounded down to the next lowest $10. Checked 2026-10-12.
South Carolina Department of Revenue: SC1040Instr_2025.pdf, South Carolina Department of Revenue. Engine 1.7.0: SC1040 line w: $4,930 per dependent and line t: $4,930 more per dependent under 6 (TY2025; the 2026 indexed amount is not published); line g: all disability retirement income of a person classified totally and permanently disabled; line p: the retirement deduction does not cover distributions with the federal premature-distribution penalty, nor an inherited IRA (the original owner's only). Checked 2026-10-12.
South Carolina Legislature: t12c006.php, South Carolina Legislature. Engine 1.7.0: SC1040 line w: $4,930 per dependent and line t: $4,930 more per dependent under 6 (TY2025; the 2026 indexed amount is not published); line g: all disability retirement income of a person classified totally and permanently disabled; line p: the retirement deduction does not cover distributions with the federal premature-distribution penalty, nor an inherited IRA (the original owner's only). Earned income credit (engine 1.12.0): 125% of the federal EIC, nonrefundable, at most $200 from 2026. Checked 2026-10-12.
South Carolina Department of Revenue: RR22-11.pdf, South Carolina Department of Revenue. Engine 1.7.0: SC1040 line w: $4,930 per dependent and line t: $4,930 more per dependent under 6 (TY2025; the 2026 indexed amount is not published); line g: all disability retirement income of a person classified totally and permanently disabled; line p: the retirement deduction does not cover distributions with the federal premature-distribution penalty, nor an inherited IRA (the original owner's only). Checked 2026-10-12.
2025 SC1040TC Tax Credits, South Carolina Department of Revenue. Earned income credit (engine 1.12.0): 125% of the federal EIC, nonrefundable, at most $200 from 2026. Checked 2026-10-12.

Age 65+ subtractions and credits

At age 65 or older: $15,000 is subtracted from the base ($30,000 for a married couple filing jointly when both qualify), against any income. With the spouse's age given, each spouse qualifies on their own age.

S.C. Code of Laws Title 12, Chapter 6 (South Carolina Income Tax Act), South Carolina General Assembly. S.C. Code 12-6-1170(B) gives each resident aged 65 or older a deduction of up to $15,000 against any income ($30,000 for a joint return when both spouses are 65+), reduced by the retirement income deduction claimed under (A). Checked 2026-10-12.
SC Revenue Ruling #22-11 (Section 12-6-1170 and 12-6-1171 deductions), South Carolina Department of Revenue. The Department's ruling describes the 65-and-older deduction as usable against any type of income. 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.

S.C. Code of Laws Title 12, Chapter 6 (South Carolina Income Tax Act), South Carolina General Assembly. S.C. Code 12-6-1120(4) computes South Carolina gross income without IRC Section 86, so Social Security benefits are fully exempt. Checked 2026-10-12.
SC Revenue Ruling #22-11 (Section 12-6-1170 and 12-6-1171 deductions), South Carolina Department of Revenue. The Department states that Section 12-6-1120(4) exempts Social Security from South Carolina tax. Checked 2026-10-12.

IRA, 401(k) and private pensions

A lower cap of $3,000 ($6,000 MFJ) applies 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 $6,000 joint cap covers pooled income.

S.C. Code of Laws Title 12, Chapter 6 (South Carolina Income Tax Act), South Carolina General Assembly. S.C. Code 12-6-1170(A) lets each original owner of a qualified retirement account deduct up to $3,000 of retirement income a year ($10,000 from the year the taxpayer reaches 65), where retirement income is otherwise-taxable income not subject to a premature-distribution penalty from IRC 401, 403, 408 and 457 plans and public employee plans. Engine 1.7.0: SC1040 line w: $4,930 per dependent and line t: $4,930 more per dependent under 6 (TY2025; the 2026 indexed amount is not published); line g: all disability retirement income of a person classified totally and permanently disabled; line p: the retirement deduction does not cover distributions with the federal premature-distribution penalty, nor an inherited IRA (the original owner's only). Checked 2026-10-12.
SC Revenue Ruling #22-11 (Section 12-6-1170 and 12-6-1171 deductions), South Carolina Department of Revenue. The $3,000 retirement income deduction is available at any age to the original owner of the retirement account. Engine 1.7.0: SC1040 line w: $4,930 per dependent and line t: $4,930 more per dependent under 6 (TY2025; the 2026 indexed amount is not published); line g: all disability retirement income of a person classified totally and permanently disabled; line p: the retirement deduction does not cover distributions with the federal premature-distribution penalty, nor an inherited IRA (the original owner's only). Checked 2026-10-12.
South Carolina Department of Revenue: SC1040Instr_2025.pdf, South Carolina Department of Revenue. Engine 1.7.0: SC1040 line w: $4,930 per dependent and line t: $4,930 more per dependent under 6 (TY2025; the 2026 indexed amount is not published); line g: all disability retirement income of a person classified totally and permanently disabled; line p: the retirement deduction does not cover distributions with the federal premature-distribution penalty, nor an inherited IRA (the original owner's only). Engine 1.8.0: a surviving spouse deducts up to $3,000 ($10,000 when the deceased spouse would have been 65) of the retirement income received as a surviving spouse (line p-3), not the own-plan deduction, and p-3 does not reduce the age 65 deduction; the deceased spouse's age is not an input, so the engine takes $3,000. A death distribution carries no premature-distribution penalty, so it is retirement income at any age. Line p-3: $3,000, or $10,000 by the deceased spouse's age had they lived (deceasedSpouseAge; engine 1.8.0 final). Checked 2026-10-12.

Public pensions

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

S.C. Code of Laws Title 12, Chapter 6 (South Carolina Income Tax Act), South Carolina General Assembly. Federal, state and local public employee pensions are retirement income under 12-6-1170(A) and draw the same $3,000 / $10,000 deduction as private plans. Checked 2026-10-12.
Individual Income Tax FAQs, South Carolina Department of Revenue. Military retirement income is fully deductible (Section 12-6-1171). Checked 2026-10-12.

Military retirement pay

Military retirement pay is fully exempt, at any age.
The military amount excluded reduces that taxpayer's general retirement-income exclusion.
The military amount excluded reduces that taxpayer's age-65 subtraction.
Rules are applied per taxpayer at that person's own age when the spouse's age is given. API value: rules.militaryRetirement.treatment: "exempt".

T12c006, South Carolina Legislature. Military retirement income is deductible in full, and the deduction reduces the retiree's own retirement and age-65 deductions. Engine 1.8.0: a surviving spouse's military survivor benefit (line p-6) reduces neither the own-plan nor the age 65 deduction. Checked 2026-10-12.
2025 SC1040 instructions, South Carolina Department of Revenue. Engine 1.8.0: line p-6, the surviving spouse military retirement deduction, does not reduce the age 65 and older deduction. 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 12-6-1170(A) deduction; the engine's treatment is an inference from the statute's definition and the 72(t) reference.

SC Information Letter #26-20 (individual income tax changes under H.4216 / Act 110), South Carolina Department of Revenue. From 2026 South Carolina starts from federal adjusted gross income, so a taxable Roth conversion enters the SC base as ordinary income. Checked 2026-10-12.
SC Revenue Ruling #22-11 (Section 12-6-1170 and 12-6-1171 deductions), South Carolina Department of Revenue. The retirement income deduction covers otherwise-taxable plan income not subject to the IRC 72(t) premature-distribution penalty, at any age; a Roth conversion is penalty-exempt IRA income, so the engine lets it draw the $3,000 deduction. Checked 2026-10-12.

Capital gains

56% of net long-term gain enters the base (44% is excluded) and is taxed at ordinary rates.
Short-term gains are ordinary income.

S.C. Code of Laws Title 12, Chapter 6 (South Carolina Income Tax Act), South Carolina General Assembly. S.C. Code 12-6-1150 allows a deduction of 44% of net capital gain, so 56% of long-term gains enters South Carolina taxable income. Checked 2026-10-12.
Individual Income Tax FAQs, South Carolina Department of Revenue. Individuals deduct 44% of net long-term capital gain recognized in South Carolina. Checked 2026-10-12.
Information Letter #26-20 (2026 individual income tax changes), South Carolina Department of Revenue. 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

The API applies these through its blind, disabled, spouse.blind and spouse.disabled fields; absent means false.

South Carolina Department of Revenue: SC1040Instr_2025.pdf, South Carolina Department of Revenue. Engine 1.7.0: SC1040 line w: $4,930 per dependent and line t: $4,930 more per dependent under 6 (TY2025; the 2026 indexed amount is not published); line g: all disability retirement income of a person classified totally and permanently disabled; line p: the retirement deduction does not cover distributions with the federal premature-distribution penalty, nor an inherited IRA (the original owner's only). Checked 2026-10-12.
South Carolina Legislature: t12c006.php, South Carolina Legislature. Engine 1.7.0: SC1040 line w: $4,930 per dependent and line t: $4,930 more per dependent under 6 (TY2025; the 2026 indexed amount is not published); line g: all disability retirement income of a person classified totally and permanently disabled; line p: the retirement deduction does not cover distributions with the federal premature-distribution penalty, nor an inherited IRA (the original owner's only). Checked 2026-10-12.
South Carolina Department of Revenue: RR22-11.pdf, South Carolina Department of Revenue. Engine 1.7.0: SC1040 line w: $4,930 per dependent and line t: $4,930 more per dependent under 6 (TY2025; the 2026 indexed amount is not published); line g: all disability retirement income of a person classified totally and permanently disabled; line p: the retirement deduction does not cover distributions with the federal premature-distribution penalty, nor an inherited IRA (the original owner's only). Checked 2026-10-12.

Part-year and nonresident returns

Part-year resident (Schedule NR): 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.
Nonresident (Schedule NR): 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.
The ratio: the federal AGI of the state's income over the federal AGI of the whole year, rounded to 2 places, at most 1.
Prorated on a part-year return: the standard deduction.
Prorated on a nonresident return: the standard deduction.
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	South Carolina's rule
One spouse a full-year resident, the other a part-year resident	a joint part-year / nonresident return is required.
One spouse a full-year resident, the other a nonresident	a joint part-year / nonresident return is required.
One spouse a part-year resident, the other a nonresident	a joint part-year / nonresident return, the only return the state's documents describe for these spouses; South Carolina's Schedule NR describes the joint return with a part-year spouse; S.C. Code 12-6-5000 makes a joint return mandatory only for residents and nonresidents, so whether separate returns are allowed is not stated.
Both part-year residents, different resident periods	a joint part-year / nonresident return, the only return the state's documents describe for these spouses; South Carolina's Schedule NR describes the joint return with each spouse's own dates; whether separate returns are allowed is not stated.
Both nonresidents, only one with income from the state	a joint part-year / nonresident return is required; S.C. Code 12-6-5000(C)(2): a nonresident whose home state does not let a South Carolina resident file jointly with a spouse files a separate return; that turns on the other state's rule, not an input (not calculated).

2025 Schedule NR Instructions (Nonresident Schedule), South Carolina Department of Revenue. Part-year / nonresident return (engine 1.12.0, residency): Schedule NR: SC taxable income = SC-column AGI (income while resident + SC-source while nonresident, line 31 col B) + SC additions - SC subtractions (dependent exemption, 44% LTCG, retirement and age-65 deductions; not prorated) - [federal standard or itemized deduction x proration %] (lines 45-47). Result goes to SC1040 line 5 and is taxed with the regular SC rate computation. Only the deduction is prorated. A part-year resident may instead elect to file as a full-year resident on all income with a credit for tax paid to the other sta Checked 2026-10-12.
2025 Schedule NR (Rev. 4/2/25), South Carolina Department of Revenue. Part-year / nonresident return (engine 1.12.0, residency): Schedule NR: SC taxable income = SC-column AGI (income while resident + SC-source while nonresident, line 31 col B) + SC additions - SC subtractions (dependent exemption, 44% LTCG, retirement and age-65 deductions; not prorated) - [federal standard or itemized deduction x proration %] (lines 45-47). Result goes to SC1040 line 5 and is taxed with the regular SC rate computation. Only the deduction is prorated. A part-year resident may instead elect to file as a full-year resident on all income with a credit for tax paid to the other sta Checked 2026-10-12.
2025 SC1040 Individual Income Tax packet (SC1040 Book), South Carolina Department of Revenue. Part-year / nonresident return (engine 1.12.0, residency): Schedule NR: SC taxable income = SC-column AGI (income while resident + SC-source while nonresident, line 31 col B) + SC additions - SC subtractions (dependent exemption, 44% LTCG, retirement and age-65 deductions; not prorated) - [federal standard or itemized deduction x proration %] (lines 45-47). Result goes to SC1040 line 5 and is taxed with the regular SC rate computation. Only the deduction is prorated. A part-year resident may instead elect to file as a full-year resident on all income with a credit for tax paid to the other sta Checked 2026-10-12.
2025 SC1040 Individual Income Tax Packet (Instructions, FAQs), South Carolina Department of Revenue. Married couples whose residency differs (engine 1.13.0): Checked 2026-10-12.
S.C. Code of Laws Title 12 Chapter 6 (South Carolina Income Tax Act), South Carolina Legislature. Married couples whose residency differs (engine 1.13.0): Checked 2026-10-12.
2025 Schedule NR Instructions (July 2025), South Carolina Department of Revenue. Married couples whose residency differs (engine 1.13.0): Checked 2026-10-12.
2025 Schedule NR (Rev. 4/2/25), South Carolina Department of Revenue. Married couples whose residency differs (engine 1.13.0): Checked 2026-10-12.

Worked examples

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

Household (engine inputs)	State tax
Single, 67: $30,000 private pension, $20,000 IRA, $10,000 interest, $24,000 Social Security ($17,000 federally taxable), $5,000 long-term gain	$1,339.43
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	$2,318.90
Single, 60: $60,000 other ordinary income and a $50,000 Roth conversion	$4,608.70
Married filing jointly, 66: $30,000 IRA, a $40,000 Roth conversion, $30,000 Social Security ($25,500 federally taxable)	$282.98
Single, 58: $36,000 military retirement pay and $30,000 wages	$439.59
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	$268.65

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: $1,339.43

Line	Amount
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	$2,800
− Standard deduction	$3,550
− Age subtractions and deductions	$15,000
= State taxable income	$44,250
Tax from the rate schedule	$1,339.43
= Tax before credits	$1,339.43
= Tax	$1,339.43

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: $2,318.90

Line	Amount
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	$5,600
− Standard deduction	$12,550
− Age subtractions and deductions	$30,000
= State taxable income	$63,050
Tax from the rate schedule	$2,318.90
= Tax before credits	$2,318.90
= Tax	$2,318.90

Single, 60: $60,000 other ordinary income and a $50,000 Roth conversion: $4,608.70

Line	Amount
Income total used by the income tests	$110,000
Retirement income and conversions excluded (not in the base)	$3,000
+ Other ordinary income in the base	$60,000
+ Retirement income in the base	$47,000
= State taxable income	$107,000
Tax from the rate schedule	$4,608.70
= Tax before credits	$4,608.70
= Tax	$4,608.70

Married filing jointly, 66: $30,000 IRA, a $40,000 Roth conversion, $30,000 Social Security ($25,500 federally taxable): $282.98

Line	Amount
Income total used by the income tests	$95,500
+ Retirement income in the base	$70,000
− Standard deduction	$25,780
− Age subtractions and deductions	$30,000
= State taxable income	$14,220
Tax from the rate schedule	$282.98
= Tax before credits	$282.98
= Tax	$282.98

Single, 58: $36,000 military retirement pay and $30,000 wages: $439.59

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	$7,910
= State taxable income	$22,090
Tax from the rate schedule	$439.59
= Tax before credits	$439.59
= Tax	$439.59

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: $268.65

Line	Amount
Income total used by the income tests	$85,500
Retirement income and conversions excluded (not in the base)	$3,000
+ Other ordinary income in the base	$10,000
+ Retirement income in the base	$47,000
− Standard deduction	$28,500
− Age subtractions and deductions	$15,000
= State taxable income	$13,500
Tax from the rate schedule	$268.65
= Tax before credits	$268.65
= Tax	$268.65

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 South Carolina'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)	Indexed: Chained CPI (BLS) under IRC 1(f), adjusted cumulatively each December 15 for the next tax year; increase capped at 4% per year; the increase rounded down to a multiple of $10.	The 2026+ brackets ($30,000 split between 1.99% and 5.21%) are indexed under § 12-6-520: cumulative chained-CPI adjustment each December 15 using IRC 1(f), capped at 4% a year, rounded to $10 (IRC 1(f)(7) rounds down). H.4216, Act No. 110 of 2026 (ratified text) (South Carolina General Assembly, legislation): 12-6-510(C) as amended: brackets indexed under 12-6-520. Quoted: "computed at the following rates with the income brackets indexed in accordance with Section 12-6-520". Checked 2026-10-12. S.C. Code § 12-6-520 (Title 12, Chapter 6) (South Carolina Legislature, statute): Bracket indexing method. Quoted: "the department shall cumulatively adjust the brackets in Section 12-6-510 using the Chained Consumer Price Index for All Consumers"; "However, the adjustment may not exceed four percent a year, and notwithstanding the rounding amount provided in (1)(f)(7), the rounding amount is ten dollars". 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.
`std_deduction_single`, `std_deduction_mfj`, `std_deduction_hoh`, `std_deduction_phaseout_start_single`, `std_deduction_phaseout_start_mfj`, `std_deduction_phaseout_start_hoh`, `std_deduction_phaseout_denom_single`, `std_deduction_phaseout_denom_mfj`, `std_deduction_phaseout_denom_hoh`	Fixed in law: held at the rules-year amount in every later year.	From 2026 the South Carolina Income Adjusted Deduction is $15,000 / $22,500 HOH / $30,000 joint, reduced by the fraction (federal AGI - $40,000 / $60,000 / $80,000) over $55,000 / $82,500 / $110,000; § 12-6-1140(15) contains no inflation adjustment. H.4216, Act No. 110 of 2026 (ratified text) (South Carolina General Assembly, legislation): New § 12-6-1140(15). Quoted: "(i) fifteen thousand dollars for taxpayers who file as single or married filing separately"; "the amount the taxpayer's federal adjusted gross income exceeds forty thousand dollars and the denominator is fifty-five thousand"; "exceeds eighty thousand dollars and the denominator is one hundred ten thousand". Checked 2026-10-12.
`dep_exemption`, `dep_extra_exemption`	Indexed: Chained CPI (BLS) under IRC 1(f), adjusted cumulatively each December 15 for the next tax year; the increase rounded down to a multiple of $10.	The dependent exemption ($4,110 base, 2017) is adjusted cumulatively each December 15 by chained CPI under IRC 1(f), rounded to $10; the extra deduction for a dependent under six equals the dependent exemption. S.C. Code § 12-6-1140(13), 12-6-1160 (Title 12, Chapter 6) (South Carolina Legislature, statute): Dependent exemption indexing and the under-six deduction. Quoted: "each December fifteenth, the department shall cumulatively adjust the deduction amount using the Chained Consumer Price Index for All Consumers"; "The deduction allowed by this section is an amount equal to the South Carolina dependent exemption allowed pursuant to Section 12-6-1140.". 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.
`dep_extra_max_age`	Attained age: the same age in every year.	The extra deduction is for a dependent who has not yet attained age six during the year (engine: 5 or younger); fixed age. S.C. Code § 12-6-1160 (Title 12, Chapter 6) (South Carolina Legislature, statute): Age wording. Quoted: "who has not yet attained the age of six years during the applicable tax year". Checked 2026-10-12.
`retirement_exclusion_partial_single`, `retirement_exclusion_partial_mfj`, `survivor_spouse_deduction`, `survivor_spouse_deduction_older`	Fixed in law: held at the rules-year amount in every later year.	Retirement income deduction of up to $3,000 (up to $10,000 from the year the owner reaches 65); a surviving spouse applies it as it applied to the deceased spouse. Nominal in § 12-6-1170(A); no inflation adjustment. S.C. Code § 12-6-1170 (Title 12, Chapter 6) (South Carolina Legislature, statute): Subsection (A). Quoted: "an annual deduction from South Carolina taxable income of not more than three thousand dollars of retirement income received"; "the taxpayer may deduct not more than ten thousand dollars of retirement income". Checked 2026-10-12.
`retirement_exclusion_min_age`, `retirement_exclusion_partial_min_age`, `survivor_spouse_older_age`, `senior_subtraction_min_age`	Attained age: the same age in every year.	Fixed age: the higher retirement deduction and the $15,000 age deduction start in the tax year the taxpayer reaches 65; the $3,000 tier has no minimum age (engine sentinel 1). S.C. Code § 12-6-1170 (Title 12, Chapter 6) (South Carolina Legislature, statute): Age wording. Quoted: "Beginning in the year in which the taxpayer reaches age sixty-five"; "Beginning for the taxable year during which a resident individual taxpayer attains the age of sixty-five years". Checked 2026-10-12.
`senior_subtraction_single`, `senior_subtraction_mfj`	Fixed in law: held at the rules-year amount in every later year.	Age-65 deduction of up to $15,000 per person ($30,000 when both spouses qualify), reduced by the retirement deduction; nominal in § 12-6-1170(B), no inflation adjustment. S.C. Code § 12-6-1170 (Title 12, Chapter 6) (South Carolina Legislature, statute): Subsection (B). Quoted: "fifteen thousand dollars in the case when only one spouse has attained the age of sixty-five years and thirty thousand dollars when both spouses have attained such age". Checked 2026-10-12.
`two_earner_credit_max_income`	Fixed in law: held at the rules-year amount in every later year.	Two wage earner credit: 0.7% of the lesser of $50,000 or the lower earner's qualified earned income; nominal in § 12-6-3330. S.C. Code § 12-6-3330 (Title 12, Chapter 6) (South Carolina Legislature, statute): Subsection (B). Quoted: "The credit is limited to seven-tenths of one percent multiplied by the lesser of: (1) fifty thousand dollars". Checked 2026-10-12.
`cap_loss_limit`, `cap_loss_limit_mfs`	Fixed in law: held at the rules-year amount in every later year.	South Carolina starts from federal taxable income concepts, 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.
`eitc_nonref_cap`	Fixed in law: held at the rules-year amount in every later year.	Act 110 of 2026 limits the SC earned income tax credit to $200 a year from tax year 2026; no adjustment clause. Information Letter #26-20 (South Carolina Department of Revenue, agency_page): The $200 cap from 2026. Quoted: "Section 12-6-510 is amended to limit the credit allowed in a year to a maximum of $200."; "These changes are effective for income tax years beginning after December 31, 2025.". Checked 2026-10-12.

Enacted for later years, not applied by the projection

From tax year 2027, each year the Board of Economic Advisors projects individual income tax revenue growth of at least 5%, the 5.21% top rate is permanently cut by the rate worth the greater of $200 million or 25% of the recurring income tax surplus (rounded up to 0.01 point) until it reaches 1.99%; then the 1.99% rate is cut the same way toward 0% and applies to all income. (2027+; conditional)
- H.4216, Act No. 110 of 2026 (ratified text) (South Carolina General Assembly, legislation): 12-6-510(C)(2)-(3). Quoted: "beginning with Tax Year 2027 and each year thereafter, the top marginal income tax rate set forth in item (1) must be decreased"; "The reduction required by this item shall continue until the top marginal income tax rate equals 1.99 percent". Checked 2026-10-12.

What the engine does not calculate, and known approximations

Tax is computed at the exact rates; below $100,000 South Carolina uses a tax table on $50/$100 rows, so the form's whole-dollar tax can differ by up to about $3.
The two wage earner credit needs each spouse's wages (the spouse object); without them it is not given. Qualified earned income is taken as wages (the IRC §62 adjustments are not inputs).
The child and dependent care credit (a share of the federal child and dependent care expenses, SC1040 line 11) needs expenses and is not calculated. Sources: SC Information Letter #26-20 (individual income tax changes under H.4216 / Act 110) (checked 2026-10-12); H.4216 (Act No. 110 of 2026), ratified text (checked 2026-10-12); Information Letter #26-20 (checked 2026-10-12); South Carolina Department of Revenue: SC1040Instr_2025.pdf (checked 2026-10-12); South Carolina Legislature: t12c006.php (checked 2026-10-12); South Carolina Department of Revenue: RR22-11.pdf (checked 2026-10-12); 2025 SC1040TC Tax Credits (checked 2026-10-12).
Married couples whose residency differs (engine 1.13.0): when one spouse is a part-year resident and the other a nonresident: South Carolina's Schedule NR describes the joint return with a part-year spouse; S.C. Code 12-6-5000 makes a joint return mandatory only for residents and nonresidents, so whether separate returns are allowed is not stated; when both spouses are part-year residents with different resident periods: South Carolina's Schedule NR describes the joint return with each spouse's own dates; whether separate returns are allowed is not stated; when both spouses are nonresidents and only one has income from the state: S.C. Code 12-6-5000(C)(2): a nonresident whose home state does not let a South Carolina resident file jointly with a spouse files a separate return; that turns on the other state's rule, not an input (not calculated). Sources: 2025 Schedule NR Instructions (Nonresident Schedule) (checked 2026-10-12); 2025 Schedule NR (Rev. 4/2/25) (checked 2026-10-12); 2025 SC1040 Individual Income Tax packet (SC1040 Book) (checked 2026-10-12); 2025 SC1040 Individual Income Tax Packet (Instructions, FAQs) (checked 2026-10-12); S.C. Code of Laws Title 12 Chapter 6 (South Carolina Income Tax Act) (checked 2026-10-12); 2025 Schedule NR Instructions (July 2025) (checked 2026-10-12); 2025 Schedule NR (Rev. 4/2/25) (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 Scenarios replay the 2025 SC1040 (lines 1, i, o, p-1 to p-5, q-1, q-2, 5, 6) and its p/q worksheets with the Act 110 figures from SC Information Letter #26-20 (federal AGI start, SCIAD, 1.99%/5.21%), and the SC1040TT table method; tests/test_state_worksheets_3.c.

Golden scenarios (hand-computed expected tax, asserted to within $1): SC01, SC02, SC03, SCCONV1, SCSP1, SCSP2.
State-specific unit tests: test_d12_conformity_states, test_conversion_on_cap_al_la_ok_sc, test_sc_per_spouse_partial_tier, test_sc, test_dependents_by_state, test_absent_is_unchanged, test_split_path_without_ages, test_more_person_edges, test_equal_ages_split_matches_legacy_split, test_military_reduces_general, test_c_states, test_sc_hoh_sciad, test_sc_sciad_rounding_and_mfs, test_sc_two_wage_earner_credit.
Structural tests covering every state: 7.
State forms and worksheets followed in the test derivations: SC1040 lines 1, i, o, 5, 6 with the 2026 SCIAD and tax computation (SC Information Letter #26-20); SC1040 instructions worksheets for lines p-1/p-2 (retirement deduction), p-4/p-5 (military) and q-1/q-2 (age 65 and older deduction); SC1040TT tax table (row-midpoint method, 2025 construction applied to the 2026 rates) and Tax Rate Schedule; SC1040 line 12 two wage earner credit (§12-6-3330).