Docs · Model reference

step-up-vs-gift-now

spec v1.0.0 · 250 open cases

Full specification JSON contract Evidence pack

Inputs

Field	Type	Valid domain
assetValue	float	10,000 – 50,000,000
costBasis	float	0 – 50,000,000
annualAppreciationPct	float	0 – 15
yearsToTransfer	int	1 – 40
heirLtcgRatePct	float	0 – 40

costBasis ≤ assetValue (loss property's §1015 dual-basis rule is a spec exclusion)
annualAppreciationPct and heirLtcgRatePct are PERCENT points, not decimals

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/step-up-vs-gift-now
{
  "assetValue": 25005000,
  "costBasis": 25000000,
  "annualAppreciationPct": 7.5,
  "yearsToTransfer": 21,
  "heirLtcgRatePct": 20
}

Response (chart arrays compacted)

{
  "ok": true,
  "model": "step-up-vs-gift-now",
  "specVersion": "1.0.0",
  "contractUrl": "/api/v1/models/step-up-vs-gift-now",
  "specUrl": "/api/v1/models/step-up-vs-gift-now/spec",
  "inputs": {
    "assetValue": 25005000,
    "costBasis": 25000000,
    "annualAppreciationPct": 7.5,
    "yearsToTransfer": 21,
    "heirLtcgRatePct": 20
  },
  "outputs": {
    "futureValue": 114183830.51858984,
    "carryoverBasis": 25000000,
    "embeddedGainIfGifted": 89183830.51858984,
    "heirTaxIfGifted": 17836766.103717968,
    "heirNetIfGifted": 96347064.41487187,
    "heirNetIfBequeathed": 114183830.51858984,
    "stepUpAdvantage": 17836766.103717968,
    "annualExclusionCovered": 19000,
    "lifetimeExemptionUsed": 24986000
  },
  "sentinels": [],
  "assumptions": [
    "Implements model spec step-up-vs-gift-now v1.0.0 (Concordance-tested: independently reimplemented from the spec).",
    "costBasis ≤ assetValue (loss property's §1015 dual-basis rule is a spec exclusion)",
    "annualAppreciationPct and heirLtcgRatePct are PERCENT points, not decimals"
  ],
  "facts": [
    {
      "id": "irs.gift.annual-exclusion.2026",
      "label": "Annual gift tax exclusion (per recipient)",
      "value": 19000,
      "period": "TY2026",
      "source": "Rev. Proc. 2025-32, section .42(1)"
    }
  ],
  "record": {
    "sha256": "92ab1b8c5a6e7821686c8cb520178cd92afc1f21e84ecd59aff806c0837030a5",
    "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.