Bond Price / YTM Calculator implementation

Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

Record owner

Guth Instruments

Lifecycle

verified-clean

Evidence ID

t6-031

Effect

Computation or source lookup only

Input and validation requirements

The instrument has a mathematically undefined input at market_yield = -1 and should reject it. Separately, the unspecified coupon and yield frequency creates materially different valid prices under annual versus semiannual conventions.

Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

{
  "inputs": {
    "mode": "price",
    "face_value": 1000,
    "coupon_rate": 0.05,
    "years_to_maturity": 5,
    "annual_coupon_frequency": 1,
    "market_yield": 0.04
  },
  "expected_outputs": {
    "price": 1044.518223,
    "current_yield": 0.047868959
  },
  "working": "C = 1000 × 0.05 = 50. Price = 50/(1.04)^1 + 50/(1.04)^2 + 50/(1.04)^3 + 50/(1.04)^4 + 50/(1.04)^5 + 1000/(1.04)^5. (1.04)^5 = 1.2166529024, so 1/(1.04)^5 = 0.8219271068. Coupon annuity factor = (1 - 0.8219271068)/0.04 = 4.451822330. Coupon PV = 50 × 4.451822330 = 222.5911165. Principal PV = 1000 × 0.8219271068 = 821.9271068. Price = 222.5911165 + 821.9271068 = 1044.5182233. Current yield = 50/1044.5182233 = 0.047868959, or 4.7868959%."
}

Other records

Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

• VERIFIED_LEDGER.json
• evidence-tranche6/tranche6-results.json