backdoor-roth

POST /api/v1/models/backdoor-roth
{
  "nondeductibleContribution": 4000,
  "existingPretaxIraBalance": 1000000,
  "marginalRate": 0.24
}

{
  "ok": true,
  "model": "backdoor-roth",
  "specVersion": "1.0.0",
  "contractUrl": "/api/v1/models/backdoor-roth",
  "specUrl": "/api/v1/models/backdoor-roth/spec",
  "inputs": {
    "nondeductibleContribution": 4000,
    "existingPretaxIraBalance": 1000000,
    "marginalRate": 0.24
  },
  "outputs": {
    "totalIraBalance": 1004000,
    "taxableFraction": 0.9960159362549801,
    "taxablePortion": 3984.06374501992,
    "taxFreePortion": 15.936254980079866,
    "taxOwed": 956.1752988047808,
    "effectiveTaxRateOnConversion": 0.2390438247011952,
    "isCleanBackdoor": false
  },
  "sentinels": [],
  "assumptions": [
    "Implements model spec backdoor-roth v1.0.0 (dual-implementation verified).",
    "nondeductibleContribution max is the TY2026 IRA limit (facts registry irs.ira.contribution-limit.2026); existingPretaxIraBalance aggregates all traditional/SEP/SIMPLE IRAs and is assumed fully pre-tax."
  ],
  "facts": [
    {
      "id": "irs.ira.contribution-limit.2026",
      "label": "Traditional/Roth IRA contribution limit",
      "value": 7500,
      "period": "TY2026",
      "source": "IRS TY2026 announcements (Notice 2025-67; Rev. Proc. 2025-32 newsroom page)"
    }
  ],
  "record": {
    "sha256": "a0a97440773de57b41b6aff4657eca9a4e19bd9894013ef2706b644e68989373",
    "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."
}