Source: https://guthlabs.ai/docs/instruments/tax-bracket-marginal-rate-estimator/implementation/

instrument implementation / implementation-contract

# Tax Bracket / Marginal Rate Estimator implementation

A source-bound implementation contract for Tax Bracket / Marginal Rate 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**: t7-065

**Effect**: Computation or source lookup only

## Input and validation requirements

Zero taxable income causes the effective-rate calculation to evaluate 0 ÷ 0, which is undefined. The instrument must not display a numeric effective rate for this case and should show N/A or reject the input.

## 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": {
    "taxable_income_usd": 0,
    "filing_status": "single",
    "tax_year": 2024,
    "marginal_convention": "rate on next dollar"
  },
  "expected_outputs": {
    "estimated_federal_tax_usd": 0,
    "marginal_rate": 0.1,
    "effective_rate": null
  },
  "reference_data": {
    "filing_status": "single",
    "tax_year": 2024,
    "rows": [
      {
        "lower_bound_usd": 0,
        "upper_bound_usd": 11600,
        "rate": 0.1,
        "source_convention": "IRS 2024 Tax Rate Schedule, widely published by IRS; 2024 federal ordinary-income brackets"
      }
    ]
  },
  "working": "Taxable income is $0. The occupied tax base is $0, so tax = $0 x 10% = $0. The next dollar would be in the first bracket, so marginal rate = 10%. Effective rate = tax/income = $0/$0, which is undefined, so return null."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/tax-bracket-marginal-rate-estimator/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/tax-bracket-marginal-rate-estimator/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/tax-bracket-marginal-rate-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-tranche7/tranche7-results.json`