Source: https://guthlabs.ai/docs/instruments/margin-vs-markup-converter/implementation/

instrument implementation / implementation-contract

# Margin vs Markup Converter implementation

A source-bound implementation contract for Margin vs Markup Converter; 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**: t4-259

**Effect**: Computation or source lookup only

## Input and validation requirements

A zero cost makes markup undefined, and an unlabelled margin value such as 50 is ambiguous between 50% and decimal 50. The converter should reject zero denominators and enforce explicit percentage units.

## 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": {
    "cost": 80,
    "price": 100,
    "currency": "USD",
    "basis": "per item"
  },
  "expected_outputs": {
    "margin_percent": 20,
    "markup_percent": 25
  },
  "working": "margin=(price-cost)/price=(100-80)/100=20/100=0.20=20%. markup=(price-cost)/cost=(100-80)/80=20/80=0.25=25%."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/margin-vs-markup-converter/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/margin-vs-markup-converter/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/margin-vs-markup-converter/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`