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

instrument / verified-clean

# Tax Bracket / Marginal Rate Estimator

The current ledger marks this instrument verified clean within the source-bound verification corpus.

Status: **VERIFIED_CLEAN**Lifecycle: **verified-clean**

## Inspectable records

[01**Overview**Purpose and lifecycle](<https://guthlabs.ai/docs/instruments/tax-bracket-marginal-rate-estimator/>)[02**Mechanism**Method and assumptions](<https://guthlabs.ai/docs/instruments/tax-bracket-marginal-rate-estimator/mechanism/>)[03**Implementation**Binding and validation](<https://guthlabs.ai/docs/instruments/tax-bracket-marginal-rate-estimator/implementation/>)[04**Qualification**Evidence and errata](<https://guthlabs.ai/docs/instruments/tax-bracket-marginal-rate-estimator/qualification/>)

## Ledger state

The current ledger marks this instrument verified clean within the source-bound verification corpus.

**Area**: Finance, Economics & Business (educational only — never individualized investment, tax, or legal advice)

**Tranche**: tranche-7

**Evidence ID**: t7-065

**Ledger rows**: 1

No ledger note is attached.

## Review findings

The core progressive-sum method is standard for estimating federal ordinary-income tax from taxable income using year- and filing-status-specific IRS brackets. The instrument should remain NEEDS_REVIEW until it specifies nonnegative-input validation, missing-table behavior, currency rounding, and the exact marginal-rate convention. The result must continue to be labeled educational and estimated, not actual tax owed or individualized tax advice.

### Formula and scope findings

- The progressive-bracket formula is standard only when each bracket contribution is calculated as max(0, min(taxable_income, upper_bound) - lower_bound) times the bracket rate; the specification does not state this piecewise constraint.

- Marginal rate is ambiguous at an exact bracket boundary. The implementation must define whether it reports the rate on the last dollar already included or the rate on the next dollar.

- The formula does not define a tax-rounding convention. Exact bracket arithmetic can produce fractional cents, while IRS calculations may use different rounding or tax-table conventions.

- Estimated federal tax owed is not actual balance due or total tax liability unless credits, withholding, deductions, AMT, and other provisions are explicitly excluded and labeled. The supplied educational disclaimer addresses much of this, but the output name remains potentially misleading.

### Unit assumptions

- Taxable income is nonnegative, annual, federal taxable income measured in U.S. dollars.

- The test vectors use the 2024 IRS federal ordinary-income rate schedules for the stated filing status; standard deduction has already been applied because the input is taxable income.

- Rates are represented as decimal fractions, such as 0.12 for 12%.

- For these test vectors, marginal rate is defined as the rate applied to the next dollar of taxable income; therefore an exact bracket boundary reports the next bracket's rate.

- Effective rate is tax divided by taxable income. It is undefined at zero income and is returned as null there.

- No interpolation is used; bracket schedules are piecewise constant.

## Boundary hardening

**BREAK_CLAIMED** · SELF_FLAGGED

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.

## Errata and corrections

No applied erratum is attached to this unique-name record.

## Inspectable example

4 review vectors are recorded. One source-bound sample is shown below.

````
{
  "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."
}
````

## Related workflows

No source-defined multi-instrument workflow membership is recorded.

## Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

- `VERIFIED_LEDGER.json · VERIFIED_CLEAN`

- `evidence-tranche7/tranche7-results.json`

- `BOUNDARY_HAZARD_CATALOG.json`