Source: https://guthlabs.ai/docs/instruments/bill-split-calculator/implementation/

instrument implementation / implementation-contract

# Bill Split Calculator implementation

A source-bound implementation contract for Bill Split Calculator; 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**: t5-121

**Effect**: Computation or source lookup only

## Input and validation requirements

The calculator has an undefined-result trap when n_people is zero and should reject that input. Its percentage fields also have a convention ambiguity: interpreting 10 as 10% gives 115 per person in the probe, while interpreting it as a raw multiplier gives 1600 per person.

## 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": "even",
    "total": 96,
    "n_people": 4
  },
  "expected_outputs": {
    "amount_owed_per_person": {
      "person_1": 24,
      "person_2": 24,
      "person_3": 24,
      "person_4": 24
    }
  },
  "working": "96.00 / 4 = 24.00. Each person owes 24.00."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/bill-split-calculator/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/bill-split-calculator/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/bill-split-calculator/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-tranche5/tranche5-results.json`