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FA-59126 / Payroll withholding rules / Open access

W-4 exempt claim expiration: expiry year · case 01

Exempt forms filed after mid-February expire immediately.

Verified by executionVariant 1 · 8 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The expiry date is set in the filing year instead of the following year.

THE FAILURE

The expiry date is set in the filing year instead of the following year.

Unsuccessful approach: The attempt anchors expiry to the pay-date year, so an old exempt form revives every January.

Case contract

Input {claims: [[[y,m,d], exempt]], pay_date [y,m,d]}. The active claim is the latest-dated claim on or before the pay date (claims processed by date; equal dates keep input order, last wins). No claim -> 'single-default'. Non-exempt claim -> 'per-form'. Exempt claim is honored through February 15 of the year after it was filed, inclusive; afterwards 'single-default'.

Why this case matters

Exempt status must lapse on a fixed date, reverting to default withholding until a new form arrives.

1 / The failure

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(x):
    pay = tuple(x['pay_date'])
    active = None
    for date, exempt in sorted(x['claims'], key=lambda c: tuple(c[0])):
        if tuple(date) <= pay:
            active = (tuple(date), exempt)
    if active is None:
        return 'single-default'
    if not active[1]:
        return 'per-form'
    expiry = (active[0][0], 2, 15)
    return 'exempt' if pay <= expiry else 'single-default'
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression', {'claims': [[[2023, 9, 19], True], [[2023, 8, 5], True], [[2022, 3, 16], False]], 'pay_date': [2023, 9, 19]}, 'exempt'), ('regression', {'claims': [[[2023, 10, 8], True], [[2024, 3, 27], True]], 'pay_date': [2023, 10, 8]}, 'exempt'), ('partial-repair probe', {'claims': [[[2022, 5, 10], True]], 'pay_date': [2022, 5, 10]}, 'exempt'), ('partial-repair probe', {'claims': [[[2023, 4, 26], True], [[2022, 11, 26], False]], 'pay_date': [2023, 4, 26]}, 'exempt'), ('normal control', {'claims': [[[2022, 2, 13], True], [[2023, 3, 1], False], [[2022, 3, 22], False]], 'pay_date': [2024, 2, 27]}, 'per-form'), ('normal control', {'claims': [[[2023, 2, 25], False]], 'pay_date': [2025, 12, 24]}, 'per-form'), ('normal control', {'claims': [], 'pay_date': [2025, 2, 4]}, 'single-default'), ('normal control', {'claims': [[[2023, 7, 12], False], [[2023, 2, 5], False], [[2024, 5, 28], False]], 'pay_date': [2024, 2, 16]}, 'per-form')], [('regression', {'claims': [[[2023, 10, 8], True], [[2024, 3, 27], True]], 'pay_date': [2023, 10, 8]}, 'exempt'), ('regression', {'claims': [[[2023, 2, 6], True]], 'pay_date': [2024, 2, 13]}, 'exempt'), ('partial-repair probe', {'claims': [[[2022, 5, 10], True]], 'pay_date': [2022, 5, 10]}, 'exempt'), ('partial-repair probe', {'claims': [[[2023, 4, 26], True], [[2022, 11, 26], False]], 'pay_date': [2023, 4, 26]}, 'exempt'), ('normal control', {'claims': [[[2022, 7, 27], False], [[2022, 1, 5], True], [[2022, 8, 16], True]], 'pay_date': [2024, 5, 27]}, 'single-default'), ('normal control', {'claims': [[[2023, 4, 5], True]], 'pay_date': [2024, 11, 6]}, 'single-default'), ('normal control', {'claims': [], 'pay_date': [2023, 2, 16]}, 'single-default'), ('normal control', {'claims': [], 'pay_date': [2023, 2, 15]}, 'single-default')], [('regression', {'claims': [[[2022, 5, 10], True]], 'pay_date': [2022, 5, 10]}, 'exempt'), ('regression', {'claims': [[[2023, 2, 6], True]], 'pay_date': [2024, 2, 13]}, 'exempt'), ('partial-repair probe', {'claims': [[[2024, 11, 25], False], [[2022, 6, 11], True], [[2024, 3, 25], True]], 'pay_date': [2024, 4, 3]}, 'exempt'), ('partial-repair probe', {'claims': [[[2022, 10, 24], True], [[2022, 6, 19], True], [[2023, 1, 23], False]], 'pay_date': [2022, 10, 24]}, 'exempt'), ('normal control', {'claims': [[[2024, 1, 17], False]], 'pay_date': [2025, 2, 16]}, 'per-form'), ('normal control', {'claims': [[[2022, 1, 6], False], [[2024, 2, 7], False]], 'pay_date': [2024, 2, 12]}, 'per-form'), ('normal control', {'claims': [[[2023, 4, 9], False], [[2024, 8, 26], False], [[2022, 5, 3], False]], 'pay_date': [2024, 7, 21]}, 'per-form'), ('normal control', {'claims': [], 'pay_date': [2023, 2, 27]}, 'single-default')], [('regression', {'claims': [[[2023, 4, 26], True], [[2022, 11, 26], False]], 'pay_date': [2023, 4, 26]}, 'exempt'), ('regression', {'claims': [[[2022, 5, 10], True]], 'pay_date': [2022, 5, 10]}, 'exempt'), ('partial-repair probe', {'claims': [[[2023, 2, 17], True], [[2024, 9, 16], False]], 'pay_date': [2023, 2, 17]}, 'exempt'), ('partial-repair probe', {'claims': [[[2022, 3, 20], True]], 'pay_date': [2025, 2, 15]}, 'single-default'), ('normal control', {'claims': [[[2024, 6, 18], True], [[2024, 1, 24], True], [[2024, 8, 3], True]], 'pay_date': [2025, 2, 16]}, 'single-default'), ('normal control', {'claims': [[[2023, 9, 14], False], [[2024, 8, 7], True], [[2024, 1, 1], True]], 'pay_date': [2023, 9, 14]}, 'per-form'), ('normal control', {'claims': [[[2023, 9, 6], True], [[2023, 1, 17], False], [[2022, 11, 5], True]], 'pay_date': [2025, 2, 16]}, 'single-default'), ('normal control', {'claims': [[[2023, 10, 8], False], [[2024, 8, 1], False]], 'pay_date': [2023, 2, 16]}, 'single-default')], [('regression', {'claims': [[[2024, 11, 25], False], [[2022, 6, 11], True], [[2024, 3, 25], True]], 'pay_date': [2024, 4, 3]}, 'exempt'), ('regression', {'claims': [[[2022, 7, 16], True], [[2024, 7, 18], True]], 'pay_date': [2025, 2, 15]}, 'exempt'), ('partial-repair probe', {'claims': [[[2023, 9, 8], True], [[2023, 6, 20], True]], 'pay_date': [2023, 9, 8]}, 'exempt'), ('partial-repair probe', {'claims': [[[2022, 10, 19], True], [[2022, 10, 27], True]], 'pay_date': [2022, 10, 19]}, 'exempt'), ('normal control', {'claims': [[[2024, 12, 15], False], [[2023, 9, 28], False]], 'pay_date': [2025, 2, 3]}, 'per-form'), ('normal control', {'claims': [], 'pay_date': [2024, 7, 6]}, 'single-default'), ('normal control', {'claims': [[[2022, 1, 12], True], [[2022, 3, 16], True]], 'pay_date': [2024, 5, 17]}, 'single-default'), ('normal control', {'claims': [[[2022, 3, 17], True]], 'pay_date': [2023, 2, 17]}, 'single-default')]]
for i, (label, args, expected) in enumerate(fixtures[N-1]):
    check("%s %d" % (label, i), solve(args), expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
Boundary fixtureActualExpectedOutcome
regression 0single-defaultexemptFailed
regression 1single-defaultexemptFailed
partial-repair probe 2single-defaultexemptFailed
partial-repair probe 3single-defaultexemptFailed
normal control 4per-formper-formPassed
normal control 5per-formper-formPassed
normal control 6single-defaultsingle-defaultPassed
normal control 7per-formper-formPassed

SHA-256 / 9a81c4957fb65200dd7fb828045424bde6d0c9e2df8fa2fbb9984f7e13d224d0

2 / The unsuccessful fix

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(x):
    pay = tuple(x['pay_date'])
    active = None
    for date, exempt in sorted(x['claims'], key=lambda c: tuple(c[0])):
        if tuple(date) <= pay:
            active = (tuple(date), exempt)
    if active is None:
        return 'single-default'
    if not active[1]:
        return 'per-form'
    expiry = (pay[0], 2, 15)
    return 'exempt' if pay <= expiry else 'single-default'
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression', {'claims': [[[2023, 9, 19], True], [[2023, 8, 5], True], [[2022, 3, 16], False]], 'pay_date': [2023, 9, 19]}, 'exempt'), ('regression', {'claims': [[[2023, 10, 8], True], [[2024, 3, 27], True]], 'pay_date': [2023, 10, 8]}, 'exempt'), ('partial-repair probe', {'claims': [[[2022, 5, 10], True]], 'pay_date': [2022, 5, 10]}, 'exempt'), ('partial-repair probe', {'claims': [[[2023, 4, 26], True], [[2022, 11, 26], False]], 'pay_date': [2023, 4, 26]}, 'exempt'), ('normal control', {'claims': [[[2022, 2, 13], True], [[2023, 3, 1], False], [[2022, 3, 22], False]], 'pay_date': [2024, 2, 27]}, 'per-form'), ('normal control', {'claims': [[[2023, 2, 25], False]], 'pay_date': [2025, 12, 24]}, 'per-form'), ('normal control', {'claims': [], 'pay_date': [2025, 2, 4]}, 'single-default'), ('normal control', {'claims': [[[2023, 7, 12], False], [[2023, 2, 5], False], [[2024, 5, 28], False]], 'pay_date': [2024, 2, 16]}, 'per-form')], [('regression', {'claims': [[[2023, 10, 8], True], [[2024, 3, 27], True]], 'pay_date': [2023, 10, 8]}, 'exempt'), ('regression', {'claims': [[[2023, 2, 6], True]], 'pay_date': [2024, 2, 13]}, 'exempt'), ('partial-repair probe', {'claims': [[[2022, 5, 10], True]], 'pay_date': [2022, 5, 10]}, 'exempt'), ('partial-repair probe', {'claims': [[[2023, 4, 26], True], [[2022, 11, 26], False]], 'pay_date': [2023, 4, 26]}, 'exempt'), ('normal control', {'claims': [[[2022, 7, 27], False], [[2022, 1, 5], True], [[2022, 8, 16], True]], 'pay_date': [2024, 5, 27]}, 'single-default'), ('normal control', {'claims': [[[2023, 4, 5], True]], 'pay_date': [2024, 11, 6]}, 'single-default'), ('normal control', {'claims': [], 'pay_date': [2023, 2, 16]}, 'single-default'), ('normal control', {'claims': [], 'pay_date': [2023, 2, 15]}, 'single-default')], [('regression', {'claims': [[[2022, 5, 10], True]], 'pay_date': [2022, 5, 10]}, 'exempt'), ('regression', {'claims': [[[2023, 2, 6], True]], 'pay_date': [2024, 2, 13]}, 'exempt'), ('partial-repair probe', {'claims': [[[2024, 11, 25], False], [[2022, 6, 11], True], [[2024, 3, 25], True]], 'pay_date': [2024, 4, 3]}, 'exempt'), ('partial-repair probe', {'claims': [[[2022, 10, 24], True], [[2022, 6, 19], True], [[2023, 1, 23], False]], 'pay_date': [2022, 10, 24]}, 'exempt'), ('normal control', {'claims': [[[2024, 1, 17], False]], 'pay_date': [2025, 2, 16]}, 'per-form'), ('normal control', {'claims': [[[2022, 1, 6], False], [[2024, 2, 7], False]], 'pay_date': [2024, 2, 12]}, 'per-form'), ('normal control', {'claims': [[[2023, 4, 9], False], [[2024, 8, 26], False], [[2022, 5, 3], False]], 'pay_date': [2024, 7, 21]}, 'per-form'), ('normal control', {'claims': [], 'pay_date': [2023, 2, 27]}, 'single-default')], [('regression', {'claims': [[[2023, 4, 26], True], [[2022, 11, 26], False]], 'pay_date': [2023, 4, 26]}, 'exempt'), ('regression', {'claims': [[[2022, 5, 10], True]], 'pay_date': [2022, 5, 10]}, 'exempt'), ('partial-repair probe', {'claims': [[[2023, 2, 17], True], [[2024, 9, 16], False]], 'pay_date': [2023, 2, 17]}, 'exempt'), ('partial-repair probe', {'claims': [[[2022, 3, 20], True]], 'pay_date': [2025, 2, 15]}, 'single-default'), ('normal control', {'claims': [[[2024, 6, 18], True], [[2024, 1, 24], True], [[2024, 8, 3], True]], 'pay_date': [2025, 2, 16]}, 'single-default'), ('normal control', {'claims': [[[2023, 9, 14], False], [[2024, 8, 7], True], [[2024, 1, 1], True]], 'pay_date': [2023, 9, 14]}, 'per-form'), ('normal control', {'claims': [[[2023, 9, 6], True], [[2023, 1, 17], False], [[2022, 11, 5], True]], 'pay_date': [2025, 2, 16]}, 'single-default'), ('normal control', {'claims': [[[2023, 10, 8], False], [[2024, 8, 1], False]], 'pay_date': [2023, 2, 16]}, 'single-default')], [('regression', {'claims': [[[2024, 11, 25], False], [[2022, 6, 11], True], [[2024, 3, 25], True]], 'pay_date': [2024, 4, 3]}, 'exempt'), ('regression', {'claims': [[[2022, 7, 16], True], [[2024, 7, 18], True]], 'pay_date': [2025, 2, 15]}, 'exempt'), ('partial-repair probe', {'claims': [[[2023, 9, 8], True], [[2023, 6, 20], True]], 'pay_date': [2023, 9, 8]}, 'exempt'), ('partial-repair probe', {'claims': [[[2022, 10, 19], True], [[2022, 10, 27], True]], 'pay_date': [2022, 10, 19]}, 'exempt'), ('normal control', {'claims': [[[2024, 12, 15], False], [[2023, 9, 28], False]], 'pay_date': [2025, 2, 3]}, 'per-form'), ('normal control', {'claims': [], 'pay_date': [2024, 7, 6]}, 'single-default'), ('normal control', {'claims': [[[2022, 1, 12], True], [[2022, 3, 16], True]], 'pay_date': [2024, 5, 17]}, 'single-default'), ('normal control', {'claims': [[[2022, 3, 17], True]], 'pay_date': [2023, 2, 17]}, 'single-default')]]
for i, (label, args, expected) in enumerate(fixtures[N-1]):
    check("%s %d" % (label, i), solve(args), expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
Boundary fixtureActualExpectedOutcome
regression 0single-defaultexemptFailed
regression 1single-defaultexemptFailed
partial-repair probe 2single-defaultexemptFailed
partial-repair probe 3single-defaultexemptFailed
normal control 4per-formper-formPassed
normal control 5per-formper-formPassed
normal control 6single-defaultsingle-defaultPassed
normal control 7per-formper-formPassed

SHA-256 / a63062bd71411c18d7c41d675f95f17025fef1235e1d073e518d220313539a94

HELD IN THE MEMBER ARCHIVE

The verified repair and its recorded checks are member-only.

This mechanism has 8 recorded checks per implementation. The open-access tier publishes the failure and the unsuccessful fix; the repaired source that passes every check, and the observations that prove it, are available to members.

Every case sharing this mechanism uses the same contract and the same repair, so this one record is held back for all of them.

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Verification & scope

A deterministic teaching model of a stipulated payroll rule with toy thresholds and rates. It makes no claim of conformance to any tax authority, statute or jurisdiction and is not payroll software. This reproducer isolates one failure mechanism. Results cover the supplied fixtures. Variants within a family share a test contract and should remain grouped when constructing evaluation splits. Related mechanisms with a shared evaluation_group must also remain together; these controlled models are not independent production incidents.

Observations recorded using Python 3.12.14 at 2026-09-29T14:46:33.355155+00:00.

Case digest / b3bbc104c9b3a15f3f685c5ae469c96d318a1960fab25b5aa9809a2d6292b9d8