Source: https://guthlabs.ai/docs/instruments/present-value-lump-sum/implementation/

instrument implementation / implementation-contract

# Present Value (Lump Sum) implementation

A source-bound implementation contract for Present Value (Lump Sum); deployment and executable qualification remain separate.

Status: **VERIFIED_CLEAN**Lifecycle: **implementation-contract**

## 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

[01**Overview**](<https://guthlabs.ai/docs/instruments/present-value-lump-sum/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/present-value-lump-sum/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/present-value-lump-sum/qualification/>)

## 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`