FAILURE MAP
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FA-62556 / Tax bracket computation / Open access

Joint filers receive the single AMT exemption · case 01

Married couples pay AMT computed with the single exemption.

Verified by executionVariant 1 · 7 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The exemption table ignores filing status.

THE FAILURE

The exemption table ignores filing status.

Unsuccessful approach: Using the joint exemption with the single phase-out threshold still misstates high-income joint filers.

Case contract

solve(amti, regular_cents, status): stipulated AMT, whole dollars. Exemption: single 85700 (phase-out threshold 609350), mfj 133300 (threshold 1218700). The exemption is reduced by 25% of AMTI above the threshold, with the reduction rounded down to whole dollars, never below 0. Base = max(0, amti - exemption). Tentative minimum tax = 26% of base up to 232600 plus 28% of base above 232600 (in cents: dollars times percent). AMT = max(0, TMT - regular tax). Return [exemption, tmt_cents, amt_cents].

Why this case matters

Tax computations hinge on which slice, threshold, ordering and rounding rule applies at each step; a misplaced boundary silently misstates liabilities.

1 / The failure

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

N = 1
observations = []
def solve(amti, regular_cents, status):
    ex, thr = (85700, 609350)
    if amti > thr: ex = max(0, ex - (amti - thr) // 4)
    base = max(0, amti - ex)
    tmt = min(base, 232600) * 26 + max(0, base - 232600) * 28
    return [ex, tmt, max(0, tmt - regular_cents)]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
cases = [[('regression status-exemption 1', (1300000, 30000000, 'mfj'), [112975, 32771500, 2771500]),
  ('regression status-exemption 2', (100000, 0, 'mfj'), [133300, 0, 0]),
  ('partial repair guard 2', (1122405, 10000000, 'mfj'), [133300, 27229740, 17229740]),
  ('control: moderate single', (200000, 2500000, 'single'), [85700, 2971800, 471800]),
  ('control: partial phase-out', (700000, 0, 'single'), [63038, 17369736, 17369736]),
  ('control: no exemption left', (1000000, 99999999, 'single'), [0, 27534800, 0]),
  ('control: odd excess', (609353, 5000000, 'single'), [85700, 14197084, 9197084])],
 [('regression status-exemption 1', (400000, 0, 'mfj'), [133300, 7002400, 7002400]),
  ('regression status-exemption 2', (365900, 35622995, 'mfj'), [133300, 6047600, 0]),
  ('partial repair guard 1', (1090557, 6893581, 'mfj'), [133300, 26337996, 19444415]),
  ('partial repair guard 2', (620628, 0, 'mfj'), [133300, 13179984, 13179984]),
  ('control: below exemption', (100000, 0, 'mfj'), [133300, 0, 0]),
  ('control: odd excess', (609353, 5000000, 'single'), [85700, 14197084, 9197084]),
  ('control: joint high', (1300000, 30000000, 'mfj'), [112975, 32771500, 2771500]),
  ('control: moderate single', (200000, 2500000, 'single'), [85700, 2971800, 471800])],
 [('regression status-exemption 1', (1122405, 10000000, 'mfj'), [133300, 27229740, 17229740]),
  ('regression status-exemption 2', (365900, 7499416, 'mfj'), [133300, 6047600, 0]),
  ('partial repair guard 1', (870886, 0, 'mfj'), [133300, 20187208, 20187208]),
  ('partial repair guard 2', (697404, 2500000, 'mfj'), [133300, 15329712, 12829712]),
  ('control: rate break', (400000, 0, 'mfj'), [133300, 7002400, 7002400]),
  ('control: moderate single', (200000, 2500000, 'single'), [85700, 2971800, 471800]),
  ('control: partial phase-out', (700000, 0, 'single'), [63038, 17369736, 17369736]),
  ('control: no exemption left', (1000000, 99999999, 'single'), [0, 27534800, 0])],
 [('regression status-exemption 1', (510076, 1928999, 'mfj'), [133300, 10084528, 8155529]),
  ('regression status-exemption 2', (318300, 22229357, 'mfj'), [133300, 4810000, 0]),
  ('partial repair guard 1', (656646, 0, 'mfj'), [133300, 14188488, 14188488]),
  ('partial repair guard 2', (1388032, 0, 'mfj'), [90967, 35852620, 35852620]),
  ('control: no exemption left', (1000000, 99999999, 'single'), [0, 27534800, 0]),
  ('control: below exemption', (100000, 0, 'mfj'), [133300, 0, 0]),
  ('control: odd excess', (609353, 5000000, 'single'), [85700, 14197084, 9197084]),
  ('control: joint high', (1300000, 30000000, 'mfj'), [112975, 32771500, 2771500])],
 [('regression status-exemption 1', (1090557, 6893581, 'mfj'), [133300, 26337996, 19444415]),
  ('regression status-exemption 2', (318300, 2500000, 'mfj'), [133300, 4810000, 2310000]),
  ('partial repair guard 1', (950664, 10000000, 'mfj'), [133300, 22420992, 12420992]),
  ('partial repair guard 2', (716795, 0, 'mfj'), [133300, 15872660, 15872660]),
  ('control: joint high', (1300000, 30000000, 'mfj'), [112975, 32771500, 2771500]),
  ('control: rate break', (400000, 0, 'mfj'), [133300, 7002400, 7002400]),
  ('control: moderate single', (200000, 2500000, 'single'), [85700, 2971800, 471800]),
  ('control: partial phase-out', (700000, 0, 'single'), [63038, 17369736, 17369736])]]
for label, args, expected in cases[N - 1]:
    check(label, 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 status-exemption 1[0, 35934800, 5934800][112975, 32771500, 2771500]Failed
regression status-exemption 2[85700, 371800, 371800][133300, 0, 0]Failed
partial repair guard 2[0, 30962140, 20962140][133300, 27229740, 17229740]Failed
control: moderate single[85700, 2971800, 471800][85700, 2971800, 471800]Passed
control: partial phase-out[63038, 17369736, 17369736][63038, 17369736, 17369736]Passed
control: no exemption left[0, 27534800, 0][0, 27534800, 0]Passed
control: odd excess[85700, 14197084, 9197084][85700, 14197084, 9197084]Passed

SHA-256 / fa89615d814573ab4b435c5940b12487965ed841cce229c928c4c5d88eebdce1

2 / The unsuccessful fix

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

N = 1
observations = []
def solve(amti, regular_cents, status):
    ex, thr = {'single': (85700, 609350), 'mfj': (133300, 609350)}[status]
    if amti > thr: ex = max(0, ex - (amti - thr) // 4)
    base = max(0, amti - ex)
    tmt = min(base, 232600) * 26 + max(0, base - 232600) * 28
    return [ex, tmt, max(0, tmt - regular_cents)]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
cases = [[('regression status-exemption 1', (1300000, 30000000, 'mfj'), [112975, 32771500, 2771500]),
  ('regression status-exemption 2', (100000, 0, 'mfj'), [133300, 0, 0]),
  ('partial repair guard 2', (1122405, 10000000, 'mfj'), [133300, 27229740, 17229740]),
  ('control: moderate single', (200000, 2500000, 'single'), [85700, 2971800, 471800]),
  ('control: partial phase-out', (700000, 0, 'single'), [63038, 17369736, 17369736]),
  ('control: no exemption left', (1000000, 99999999, 'single'), [0, 27534800, 0]),
  ('control: odd excess', (609353, 5000000, 'single'), [85700, 14197084, 9197084])],
 [('regression status-exemption 1', (400000, 0, 'mfj'), [133300, 7002400, 7002400]),
  ('regression status-exemption 2', (365900, 35622995, 'mfj'), [133300, 6047600, 0]),
  ('partial repair guard 1', (1090557, 6893581, 'mfj'), [133300, 26337996, 19444415]),
  ('partial repair guard 2', (620628, 0, 'mfj'), [133300, 13179984, 13179984]),
  ('control: below exemption', (100000, 0, 'mfj'), [133300, 0, 0]),
  ('control: odd excess', (609353, 5000000, 'single'), [85700, 14197084, 9197084]),
  ('control: joint high', (1300000, 30000000, 'mfj'), [112975, 32771500, 2771500]),
  ('control: moderate single', (200000, 2500000, 'single'), [85700, 2971800, 471800])],
 [('regression status-exemption 1', (1122405, 10000000, 'mfj'), [133300, 27229740, 17229740]),
  ('regression status-exemption 2', (365900, 7499416, 'mfj'), [133300, 6047600, 0]),
  ('partial repair guard 1', (870886, 0, 'mfj'), [133300, 20187208, 20187208]),
  ('partial repair guard 2', (697404, 2500000, 'mfj'), [133300, 15329712, 12829712]),
  ('control: rate break', (400000, 0, 'mfj'), [133300, 7002400, 7002400]),
  ('control: moderate single', (200000, 2500000, 'single'), [85700, 2971800, 471800]),
  ('control: partial phase-out', (700000, 0, 'single'), [63038, 17369736, 17369736]),
  ('control: no exemption left', (1000000, 99999999, 'single'), [0, 27534800, 0])],
 [('regression status-exemption 1', (510076, 1928999, 'mfj'), [133300, 10084528, 8155529]),
  ('regression status-exemption 2', (318300, 22229357, 'mfj'), [133300, 4810000, 0]),
  ('partial repair guard 1', (656646, 0, 'mfj'), [133300, 14188488, 14188488]),
  ('partial repair guard 2', (1388032, 0, 'mfj'), [90967, 35852620, 35852620]),
  ('control: no exemption left', (1000000, 99999999, 'single'), [0, 27534800, 0]),
  ('control: below exemption', (100000, 0, 'mfj'), [133300, 0, 0]),
  ('control: odd excess', (609353, 5000000, 'single'), [85700, 14197084, 9197084]),
  ('control: joint high', (1300000, 30000000, 'mfj'), [112975, 32771500, 2771500])],
 [('regression status-exemption 1', (1090557, 6893581, 'mfj'), [133300, 26337996, 19444415]),
  ('regression status-exemption 2', (318300, 2500000, 'mfj'), [133300, 4810000, 2310000]),
  ('partial repair guard 1', (950664, 10000000, 'mfj'), [133300, 22420992, 12420992]),
  ('partial repair guard 2', (716795, 0, 'mfj'), [133300, 15872660, 15872660]),
  ('control: joint high', (1300000, 30000000, 'mfj'), [112975, 32771500, 2771500]),
  ('control: rate break', (400000, 0, 'mfj'), [133300, 7002400, 7002400]),
  ('control: moderate single', (200000, 2500000, 'single'), [85700, 2971800, 471800]),
  ('control: partial phase-out', (700000, 0, 'single'), [63038, 17369736, 17369736])]]
for label, args, expected in cases[N - 1]:
    check(label, 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 status-exemption 1[0, 35934800, 5934800][112975, 32771500, 2771500]Failed
regression status-exemption 2[133300, 0, 0][133300, 0, 0]Passed
partial repair guard 2[5037, 30821104, 20821104][133300, 27229740, 17229740]Failed
control: moderate single[85700, 2971800, 471800][85700, 2971800, 471800]Passed
control: partial phase-out[63038, 17369736, 17369736][63038, 17369736, 17369736]Passed
control: no exemption left[0, 27534800, 0][0, 27534800, 0]Passed
control: odd excess[85700, 14197084, 9197084][85700, 14197084, 9197084]Passed

SHA-256 / e76a023429b1b35d33ae1e877a5fd8f04e18011a9cef64823e6dcbb18bb294a5

HELD IN THE MEMBER ARCHIVE

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

This mechanism has 7 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, bounded teaching model with a stipulated toy contract; it makes no claim of conformance to any real regulation, standard, or institution's rules. 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 2026-09-29T14:47:05.762798+00:00.

Case digest / 44ab2abea8573703b281483b03088eed65a381fdf897f1927da1c81b989df954