Source: https://guthlabs.ai/docs/instruments/debt-to-income-ratio-calculator/implementation/

instrument implementation / implementation-contract

# Debt-to-Income Ratio Calculator implementation

A source-bound implementation contract for Debt-to-Income Ratio 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**: t5-217

**Effect**: Computation or source lookup only

## Input and validation requirements

A zero gross monthly income produces an undefined division; an implementation that does not reject it may expose Infinity or an invalid DTI percentage.

## 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": {
    "monthly_debt_payments": [
      1500,
      300,
      200
    ],
    "gross_monthly_income": 5000
  },
  "expected_outputs": {
    "total_monthly_debt_payments": 2000,
    "dti_percent": 40,
    "threshold_note": "Illustrative reference only: 36% and 43%; actual lender criteria vary."
  },
  "working": "1. Sum debt payments: 1,500 + 300 + 200 = 2,000. 2. Divide by gross monthly income: 2,000 ÷ 5,000 = 0.40. 3. Convert to a percentage: 0.40 × 100 = 40%. 4. Result: DTI = 40%."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/debt-to-income-ratio-calculator/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/debt-to-income-ratio-calculator/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/debt-to-income-ratio-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`