Inputs
| Field | Type | Valid domain |
|---|---|---|
| ordinaryTaxableIncome | float | 0 – 1,000,000 |
| shortTermGain | float | 0 – 500,000 |
| longTermGain | float | 0 – 2,000,000 |
| filingStatus | choice | single | married |
- Gains only — loss netting and carryforwards are out of scope. NIIT MAGI is approximated by taxable income + gains, which can understate NIIT near the threshold (spec exclusion).
All fields required. Out-of-domain values are rejected with per-field errors — never clamped. Unknown fields are rejected.
Live example — generated from the real engine
Request
POST /api/v1/models/capital-gains
{
"ordinaryTaxableIncome": 500000,
"shortTermGain": 250000,
"longTermGain": 1000000,
"filingStatus": "single"
}Response (chart arrays compacted)
{
"ok": true,
"model": "capital-gains",
"specVersion": "1.0.0",
"contractUrl": "/api/v1/models/capital-gains",
"specUrl": "/api/v1/models/capital-gains/spec",
"inputs": {
"ordinaryTaxableIncome": 500000,
"shortTermGain": 250000,
"longTermGain": 1000000,
"filingStatus": "single"
},
"outputs": {
"shortTermTax": 89688,
"longTermTax": 200000,
"ltZeroRateAmount": 0,
"ltFifteenRateAmount": 0,
"ltTwentyRateAmount": 1000000,
"niit": 47500,
"totalTax": 337188,
"effectiveLongTermRateExNiit": 0.2,
"afterTaxGain": 912812
},
"sentinels": [],
"assumptions": [
"Implements model spec capital-gains v1.0.0 (dual-implementation verified).",
"Gains only — loss netting and carryforwards are out of scope. NIIT MAGI is approximated by taxable income + gains, which can understate NIIT near the threshold (spec exclusion)."
],
"facts": [
{
"id": "irs.brackets.single.top-of-10pct.2026",
"label": "Top of 10% ordinary bracket, single (vintage marker for the TY2026 table)",
"value": 12400,
"period": "TY2026",
"source": "IRS TY2026 inflation adjustments (Rev. Proc. 2025-32)"
},
{
"id": "irs.brackets.mfj.top-of-10pct.2026",
"label": "Top of 10% ordinary bracket, MFJ (vintage marker for the TY2026 table)",
"value": 24800,
"period": "TY2026",
"source": "IRS TY2026 inflation adjustments (Rev. Proc. 2025-32)"
},
{
"id": "irs.ltcg.zero-rate-top.single.2026",
"label": "LTCG maximum zero-rate amount, single (§1(h), §1(j)(5))",
"value": 49450,
"period": "TY2026",
"source": "IRS Rev. Proc. 2025-32, §.03 Maximum Capital Gains Rate"
},
{
"id": "irs.ltcg.zero-rate-top.mfj.2026",
"label": "LTCG maximum zero-rate amount, married filing jointly (§1(h), §1(j)(5))",
"value": 98900,
"period": "TY2026",
"source": "IRS Rev. Proc. 2025-32, §.03 Maximum Capital Gains Rate"
},
{
"id": "irs.niit.rate",
"label": "Net investment income tax rate",
"value": 0.038,
"period": "2013+ (IRC §1411, permanent)",
"source": "IRC §1411; IRS Topic 559 (Net Investment Income Tax)"
},
{
"id": "irs.niit.threshold.single",
"label": "NIIT MAGI threshold, single (statutory, not inflation-indexed)",
"value": 200000,
"period": "2013+ (IRC §1411, permanent)",
"source": "IRC §1411(b); IRS Topic 559"
},
{
"id": "irs.niit.threshold.mfj",
"label": "NIIT MAGI threshold, married filing jointly (statutory, not inflation-indexed)",
"value": 250000,
"period": "2013+ (IRC §1411, permanent)",
"source": "IRC §1411(b); IRS Topic 559"
}
],
"record": {
"sha256": "211671d1480fd37c962117d5c8c133eb3edbc0de1d1fc3eaf863508ba519385d",
"fields": [
"model",
"specVersion",
"inputs",
"outputs"
],
"howToVerify": "Store this record with any advice or agent output built on these numbers. To verify later: build {model, specVersion, inputs, outputs} from the stored response, serialize as JSON with object keys sorted recursively (no whitespace), and SHA-256 it — a match proves the numbers came from this spec version with these inputs, unaltered."
},
"disclaimer": "Illustrative planning model, not financial advice. Outputs follow the published model spec exactly; read the spec for assumptions and exclusions before relying on any number."
}This example is executed against the production engine when the page builds — it cannot drift from the API's real behavior.