{
  "tool_id": "art-339-compute-gross-to-net",
  "note": "golden_hash filled by golden-parity.test.mjs --update. Vector 1: standard biweekly, well below both FICA thresholds. Vector 2: crosses the 2025 Social Security wage base ($176,100) mid-period. Vector 3: crosses the $200,000 Additional Medicare Tax threshold mid-period. Vector 4: zero-wage edge (finite gate).",
  "vectors": [
    {
      "name": "standard_below_thresholds",
      "description": "$3,000 gross, $200 pretax 401(k)/HSA (FICA+FIT exempt), $300 federal withholding (declared input), $50 post-tax deduction, $10,000 YTD FICA wages before this period (well under both the $176,100 SS wage base and the $200,000 Additional Medicare threshold). FICA wages = $2,800. SS tax = 2800*0.062=$173.60. Medicare = 2800*0.0145=$40.60. Net = 3000-200-300-214.20-50=$2,235.80.",
      "policy_parameters": {
        "gross_wages_per_period": 3000,
        "federal_withholding_per_period": 300,
        "pretax_reduces_fica_and_fit": 200,
        "post_tax_other_deductions": 50,
        "ytd_fica_wages_before_period": 10000
      },
      "output_payload": {
        "net_pay": 2235.8,
        "fica_wages_this_period": 2800,
        "social_security_tax": 173.6,
        "ss_taxable_wages_this_period": 2800,
        "medicare_tax": 40.6,
        "additional_medicare_tax": 0,
        "additional_medicare_wages_this_period": 0,
        "fica_tax_total": 214.2,
        "federal_withholding_per_period": 300,
        "pretax_reduces_fica_and_fit": 200,
        "post_tax_other_deductions": 50,
        "ytd_fica_wages_after_period": 12800,
        "ss_wage_base": 176100,
        "additional_medicare_threshold": 200000,
        "constants_version": "2025",
        "regulatory_basis": "IRC 3101/3121 (FICA); SSA 2025 Contribution and Benefit Base ($176,100 OASDI wage base); IRC 3101(b)(2) Additional Medicare Tax ($200,000 employer-withholding threshold).",
        "note": "Federal FICA and net pay only; not tax advice. State/local withholding and state disability/unemployment employee contributions out of scope. federal_withholding_per_period is a declared input (e.g. from compute_federal_withholding), not recomputed here."
      },
      "compliance_flags": [
        "FEDERAL_ONLY_NOT_TAX_ADVICE"
      ],
      "golden_hash": "5dc828807d358ef437698dd1dc37dc962d0b90d54a9bec4cadd4129f7983a64e"
    },
    {
      "name": "ss_wage_base_boundary",
      "description": "$5,000 gross, $174,000 YTD FICA wages before this period. SS wage base is $176,100, so only $2,100 of this period's $5,000 is SS-taxable ($176,100-$174,000); the remaining $2,900 is SS-exempt for the rest of the year. SS tax = 2100*0.062=$130.20. Medicare has no cap: 5000*0.0145=$72.50. SS_WAGE_BASE_REACHED flags.",
      "policy_parameters": {
        "gross_wages_per_period": 5000,
        "federal_withholding_per_period": 800,
        "pretax_reduces_fica_and_fit": 0,
        "post_tax_other_deductions": 0,
        "ytd_fica_wages_before_period": 174000
      },
      "output_payload": {
        "net_pay": 3997.3,
        "fica_wages_this_period": 5000,
        "social_security_tax": 130.2,
        "ss_taxable_wages_this_period": 2100,
        "medicare_tax": 72.5,
        "additional_medicare_tax": 0,
        "additional_medicare_wages_this_period": 0,
        "fica_tax_total": 202.7,
        "federal_withholding_per_period": 800,
        "pretax_reduces_fica_and_fit": 0,
        "post_tax_other_deductions": 0,
        "ytd_fica_wages_after_period": 179000,
        "ss_wage_base": 176100,
        "additional_medicare_threshold": 200000,
        "constants_version": "2025",
        "regulatory_basis": "IRC 3101/3121 (FICA); SSA 2025 Contribution and Benefit Base ($176,100 OASDI wage base); IRC 3101(b)(2) Additional Medicare Tax ($200,000 employer-withholding threshold).",
        "note": "Federal FICA and net pay only; not tax advice. State/local withholding and state disability/unemployment employee contributions out of scope. federal_withholding_per_period is a declared input (e.g. from compute_federal_withholding), not recomputed here."
      },
      "compliance_flags": [
        "FEDERAL_ONLY_NOT_TAX_ADVICE",
        "SS_WAGE_BASE_REACHED"
      ],
      "golden_hash": "8cf8afa4b2fa70738067a5b02ca628078afbc01f57ed0e62bf5f3ece4d9f9cf1"
    },
    {
      "name": "additional_medicare_boundary",
      "description": "$10,000 gross, $195,000 YTD FICA wages before this period. The $200,000 Additional Medicare threshold falls mid-period: $5,000 of this period's wages ($195,000+$10,000-$200,000) are subject to the extra 0.9%, regardless of filing status (employer withholding rule). SS is already fully exhausted (YTD > $176,100), so SS tax = $0. Medicare = 10000*0.0145=$145. Additional Medicare = 5000*0.009=$45.",
      "policy_parameters": {
        "gross_wages_per_period": 10000,
        "federal_withholding_per_period": 2000,
        "pretax_reduces_fica_and_fit": 0,
        "post_tax_other_deductions": 0,
        "ytd_fica_wages_before_period": 195000
      },
      "output_payload": {
        "net_pay": 7810,
        "fica_wages_this_period": 10000,
        "social_security_tax": 0,
        "ss_taxable_wages_this_period": 0,
        "medicare_tax": 145,
        "additional_medicare_tax": 45,
        "additional_medicare_wages_this_period": 5000,
        "fica_tax_total": 190,
        "federal_withholding_per_period": 2000,
        "pretax_reduces_fica_and_fit": 0,
        "post_tax_other_deductions": 0,
        "ytd_fica_wages_after_period": 205000,
        "ss_wage_base": 176100,
        "additional_medicare_threshold": 200000,
        "constants_version": "2025",
        "regulatory_basis": "IRC 3101/3121 (FICA); SSA 2025 Contribution and Benefit Base ($176,100 OASDI wage base); IRC 3101(b)(2) Additional Medicare Tax ($200,000 employer-withholding threshold).",
        "note": "Federal FICA and net pay only; not tax advice. State/local withholding and state disability/unemployment employee contributions out of scope. federal_withholding_per_period is a declared input (e.g. from compute_federal_withholding), not recomputed here."
      },
      "compliance_flags": [
        "FEDERAL_ONLY_NOT_TAX_ADVICE",
        "SS_WAGE_BASE_REACHED",
        "ADDITIONAL_MEDICARE_APPLIED"
      ],
      "golden_hash": "7d39f601775581d080f5f170134ef5c7835b80c6ab8679f5e8af8da6c05a95b4"
    },
    {
      "name": "zero_wages_edge",
      "description": "Zero gross wages this period. Finite gate: every downstream figure resolves to 0, never NaN/Infinity.",
      "policy_parameters": {
        "gross_wages_per_period": 0,
        "federal_withholding_per_period": 0,
        "pretax_reduces_fica_and_fit": 0,
        "post_tax_other_deductions": 0,
        "ytd_fica_wages_before_period": 0
      },
      "output_payload": {
        "net_pay": 0,
        "fica_wages_this_period": 0,
        "social_security_tax": 0,
        "ss_taxable_wages_this_period": 0,
        "medicare_tax": 0,
        "additional_medicare_tax": 0,
        "additional_medicare_wages_this_period": 0,
        "fica_tax_total": 0,
        "federal_withholding_per_period": 0,
        "pretax_reduces_fica_and_fit": 0,
        "post_tax_other_deductions": 0,
        "ytd_fica_wages_after_period": 0,
        "ss_wage_base": 176100,
        "additional_medicare_threshold": 200000,
        "constants_version": "2025",
        "regulatory_basis": "IRC 3101/3121 (FICA); SSA 2025 Contribution and Benefit Base ($176,100 OASDI wage base); IRC 3101(b)(2) Additional Medicare Tax ($200,000 employer-withholding threshold).",
        "note": "Federal FICA and net pay only; not tax advice. State/local withholding and state disability/unemployment employee contributions out of scope. federal_withholding_per_period is a declared input (e.g. from compute_federal_withholding), not recomputed here."
      },
      "compliance_flags": [
        "FEDERAL_ONLY_NOT_TAX_ADVICE",
        "GROSS_TO_NET_ZERO_WAGES"
      ],
      "golden_hash": "58dddee02b6c3b9bd3e51d0e5440cecc1dfcc8ae83e52ccbad9ee1486d92c0e0"
    }
  ]
}