Source: https://guthlabs.ai/docs/instruments/paycheck-take-home-pay-estimator/mechanism/

instrument mechanism / verified-clean

# Paycheck / Take-Home Pay Estimator mechanism

The inspectable method record for Paycheck / Take-Home Pay Estimator, kept separate from implementation and qualification.

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

## Model scope

The catalog formula is not ready for an unqualified PASS. The main defects are the incomplete FICA statement, unspecified treatment of deduction types, and insufficient W-4/state inputs. The four vectors use 2024, single-filer, Texas, annualized educational assumptions and are intended as verification fixtures, not a substitute for the actual IRS or state withholding procedure.

- The stated FICA formula, "7.65% to cap," is incomplete and misleading: Social Security is 6.2% only up to the annual wage base, while Medicare is 1.45% with no wage cap; Additional Medicare Tax of 0.9% may apply above statutory thresholds.

- The formula subtracts pre-tax deductions after calculating withholding without specifying which deductions reduce federal income-tax wages, which reduce state wages, and which remain subject to FICA. Traditional 401(k) contributions generally reduce federal income-tax wages but remain subject to Social Security and Medicare; HSA treatment depends on payroll arrangement and jurisdiction.

- Federal withholding cannot be determined from gross pay and filing status alone. The IRS W-4 year, pay-period wages, Step 2 checkbox, dependents credit, other income, other adjustments, and extra withholding are missing.

- State withholding requires a year-dated state table and additional state-specific inputs. State alone is insufficient; some states require allowances, filing status distinctions, local taxes, or reciprocity information.

- The formula does not specify whether amounts are rounded per paycheck, whether annualized withholding is used, or how irregular pay, bonuses, multiple jobs, and wage-base tracking are handled.

- The test calculations below use a clearly stated educational annualized-tax convention for federal estimates. That convention is not identical to every employer's IRS percentage-method withholding calculation, so the instrument must not label these outputs as exact payroll withholding.

## Units and conventions

- All monetary inputs and outputs are U.S. dollars for the stated pay period unless explicitly marked annual.

- The worked vectors use 2024 federal parameters: single-filer standard deduction of $14,600, 2024 single-filer tax brackets, Social Security rate 6.2%, Medicare rate 1.45%, and Social Security wage base $168,600.

- For the annualized examples, annual gross pay equals per-pay-period gross multiplied by the number of periods: 52 weekly, 26 biweekly, or 1 annual.

- Texas is used for every state example; state withholding is assumed to be zero because Texas has no individual state income tax.

- Traditional 401(k) deductions reduce federal income-tax wages but remain subject to Social Security and Medicare in the examples.

- Federal amounts for periodic examples are annualized federal income-tax estimates divided by the number of pay periods, with final results rounded to cents.

## Inspectable vector

One of 4 source-bound review vectors:

````
{
  "inputs": {
    "gross_pay": 100,
    "pay_frequency": "weekly",
    "pay_periods_per_year": 52,
    "filing_status": "single",
    "state": "TX",
    "pre_tax_deductions": 0,
    "deduction_type": "none",
    "tax_year": 2024
  },
  "expected_outputs": {
    "federal_withholding": 0,
    "social_security": 6.2,
    "medicare": 1.45,
    "fica_total": 7.65,
    "state_withholding": 0,
    "pre_tax_deductions": 0,
    "estimated_net_pay": 92.35
  },
  "reference_data": {
    "federal_standard_deduction_single_2024": {
      "value": 14600,
      "source_convention": "IRS 2024 federal tax parameters"
    },
    "federal_single_bracket_0_to_11600": {
      "rate": 0.1,
      "source_convention": "IRS 2024 federal tax brackets"
    },
    "texas_individual_income_tax": {
      "value": 0,
      "source_convention": "Texas Comptroller statutory convention: Texas has no individual state income tax"
    },
    "social_security_rate": {
      "value": 0.062,
      "source_convention": "IRS/SSA 2024 payroll-tax convention"
    },
    "medicare_rate": {
      "value": 0.0145,
      "source_convention": "IRS/SSA 2024 payroll-tax convention"
    }
  },
  "working": "Annualized gross = $100 × 52 = $5,200. Annualized federal taxable income = max($5,200 − $14,600, 0) = $0, so federal withholding = $0. Social Security = $100 × 6.2% = $6.20. Medicare = $100 × 1.45% = $1.45. FICA = $6.20 + $1.45 = $7.65. Texas withholding = $0. Net pay = $100 − $0 − $7.65 − $0 − $0 = $92.35. The $7.65 result is the widely memorized combined employee FICA rate on wages below the Social Security cap."
}
````

## Failure boundary

**BREAK_CLAIMED** · SELF_FLAGGED

The specified instrument cannot produce complete nonzero paycheck results without year-stamped federal and state lookup tables. It also has a definite undefined-result trap when the pay-period denominator is zero, and it has a convention-sensitive deduction sign that can change the result by $400 in the probe.

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/paycheck-take-home-pay-estimator/>)[03**Implementation**](<https://guthlabs.ai/docs/instruments/paycheck-take-home-pay-estimator/implementation/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/paycheck-take-home-pay-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`

- `BOUNDARY_HAZARD_CATALOG.json`