Present Value (Lump Sum) 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

t2-008

Effect

Computation or source lookup only

Input and validation requirements

The formula reaches an undefined division-by-zero result when rate = -compounds_per_year, and the specification does not state validation or rejection behavior. Rate-unit ambiguity can also change the result by a large factor.

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": {
    "FV": 10000,
    "rate": 0.05,
    "compounds_per_year": 4,
    "years": 3
  },
  "expected_outputs": {
    "PV": 8615.09,
    "discount_factor": 0.8615086
  },
  "working": "r/n=0.05/4=0.0125. nt=4*3=12. 1+r/n=1.0125. (1.0125)^12=1.1607545177. discount factor=1/1.1607545177=0.8615086. PV=10000*0.8615086=8615.086, which rounds to 8615.09."
}

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-tranche2/tranche2-results.json