Source: https://guthlabs.ai/docs/instruments/closing-costs-cash-to-close-estimator/implementation/

instrument implementation / implementation-contract

# Closing Costs & Cash-to-Close Estimator implementation

A source-bound implementation contract for Closing Costs & Cash-to-Close Estimator; 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**: t4-044

**Effect**: Computation or source lookup only

## Input and validation requirements

An extreme but numerically valid JavaScript input produces 2e308, which overflows to Infinity. The estimator should reject, cap, or otherwise handle non-finite results rather than displaying Infinity as a cash-to-close amount.

## 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": {
    "currency": "USD",
    "purchase_price": 400000,
    "down_percent": 20,
    "closing_cost_mode": "percent_of_loan",
    "closing_cost_rate_percent": 3,
    "credits": 2500
  },
  "expected_outputs": {
    "down_payment": 80000,
    "loan_amount": 320000,
    "closing_costs": 9600,
    "credits": 2500,
    "cash_to_close": 87100
  },
  "working": "down_payment = 400000 × 20 ÷ 100 = 80000; loan_amount = 400000 - 80000 = 320000; closing_costs = 320000 × 3 ÷ 100 = 9600; cash_to_close = 80000 + 9600 - 2500 = 87100."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/closing-costs-cash-to-close-estimator/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/closing-costs-cash-to-close-estimator/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/closing-costs-cash-to-close-estimator/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`