Source: https://guthlabs.ai/docs/instruments/compound-interest-visualizer/implementation/

instrument implementation / implementation-contract

# Compound Interest Visualizer implementation

A source-bound implementation contract for Compound Interest Visualizer; 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**: t4-068

**Effect**: Computation or source lookup only

## Input and validation requirements

The stated formula is undefined when compounding_freq = 0 and is also literally undefined at rate = 0 unless the implementation supplies the zero-rate limiting branch. Rate-unit ambiguity can additionally change the result from 1150 to 6100 for the same displayed input 5.

## 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": {
    "principal": 10000,
    "contribution": 200,
    "rate": 0.05,
    "years": 3,
    "compounding_freq": 1
  },
  "expected_outputs": {
    "FV": 12206.75,
    "invested_total": 10600,
    "interest": 1606.75
  },
  "working": "q=r/n=0.05/1=0.05. Periods=n*t=1*3=3. Growth factor=(1+q)^periods=1.05^3=1.157625. Principal growth=10000*1.157625=11576.25. Contribution factor=(1.157625-1)/0.05=0.157625/0.05=3.1525. Contribution growth=200*3.1525=630.50. FV=11576.25+630.50=12206.75. Invested total=10000+(200*3)=10600. Interest=12206.75-10600=1606.75."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/compound-interest-visualizer/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/compound-interest-visualizer/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/compound-interest-visualizer/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-tranche4/tranche4-results.json`