Source: https://guthlabs.ai/docs/instruments/pricing-discount-markdown-calculator/implementation/

instrument implementation / implementation-contract

# Pricing/Discount & Markdown Calculator implementation

A source-bound implementation contract for Pricing/Discount & Markdown 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**: t4-270

**Effect**: Computation or source lookup only

## Input and validation requirements

A zero list price produces undefined required discount and undefined effective discount because the formulas divide by list price. The instrument should reject the input or display an explicit undefined result.

## 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": {
    "list_price": 100,
    "discount_percent": 20,
    "stacking": false,
    "target_price": 80
  },
  "expected_outputs": {
    "final_price": 80,
    "total_dollar_off": 20,
    "effective_discount_percent": 20,
    "required_discount_percent": 20
  },
  "working": "Sale price = 100 * (1 - 20/100) = 100 * 0.80 = 80. Total $ off = 100 - 80 = 20. Effective discount = (20/100) * 100% = 20%. Required discount to reach 80 = (1 - 80/100) * 100% = 20%."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/pricing-discount-markdown-calculator/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/pricing-discount-markdown-calculator/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/pricing-discount-markdown-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-tranche4/tranche4-results.json`