FA-62796 / Tax bracket computation / Open access

The gliding cap is applied to the whole income tax · case 01

Filers just above the limit pay the full 5.5% surcharge.

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

ROOT CAUSE

The 11.9% cap is computed on the whole tax rather than on the excess over the limit.

THE FAILURE

The 11.9% cap is computed on the whole tax rather than on the excess over the limit.

Unsuccessful approach: Charging 11.9% of the excess without comparing to 5.5% of the tax over-charges high incomes.

Case contract

solve(income_tax, joint): stipulated surcharge on income tax, in integer cents. The exemption limit is 1813000 (doubled for joint assessment). At or below it the surcharge is 0; above it the surcharge is the lesser of 5.5% of the income tax and 11.9% of the excess over the limit (a gliding zone), rounded down to 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
from fractions import Fraction
N = 1
observations = []
def solve(income_tax, joint):
    thr = 1813000 * (2 if joint else 1)
    if income_tax <= thr: return 0
    soli = min(income_tax * Fraction(55, 1000), income_tax * Fraction(119, 1000))
    return int(soli)
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
cases = [[('regression glide-base 1', (1900000, False), 10353), ('regression glide-base 2', (3700000, True), 8806),
  ('partial repair guard 1', (5000000, False), 275000), ('partial repair guard 2', (3626001, False), 199430),
  ('control: at limit', (1813000, False), 0), ('control: joint below', (3000000, True), 0),
  ('control: glide edge', (3300000, False), 176953)],
 [('regression glide-base 1', (3300000, False), 176953), ('regression glide-base 2', (1813009, False), 1),
  ('partial repair guard 1', (3835420, False), 210948), ('partial repair guard 2', (3974588, False), 218602),
  ('control: joint glide', (3700000, True), 8806), ('control: joint below', (3000000, True), 0),
  ('control: at limit', (1813000, False), 0), ('control: gliding zone', (1900000, False), 10353)],
 [('regression glide-base 1', (1983210, False), 20254), ('regression glide-base 2', (1813001, False), 0),
  ('partial repair guard 1', (3508965, False), 192993), ('partial repair guard 2', (3491244, False), 192018),
  ('control: at limit', (1813000, False), 0), ('control: gliding zone', (1900000, False), 10353),
  ('control: full rate', (5000000, False), 275000), ('control: joint glide', (3700000, True), 8806)],
 [('regression glide-base 1', (3626001, True), 0), ('regression glide-base 2', (4499538, True), 103951),
  ('partial repair guard 1', (3409571, False), 187526), ('partial repair guard 2', (4398816, False), 241934),
  ('control: joint glide', (3700000, True), 8806), ('control: joint below', (3000000, True), 0),
  ('control: glide edge', (3300000, False), 176953), ('control: at limit', (1813000, False), 0)],
 [('regression glide-base 1', (3256603, False), 171788), ('regression glide-base 2', (2115665, False), 36017),
  ('partial repair guard 1', (5112893, False), 281209), ('partial repair guard 2', (4374325, False), 240587),
  ('control: at limit', (1813000, False), 0), ('control: gliding zone', (1900000, False), 10353),
  ('control: full rate', (5000000, False), 275000), ('control: joint glide', (3700000, True), 8806)]]
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 fixture	Actual	Expected	Outcome
regression glide-base 1	`104500`	`10353`	Failed
regression glide-base 2	`203500`	`8806`	Failed
partial repair guard 1	`275000`	`275000`	Passed
partial repair guard 2	`199430`	`199430`	Passed
control: at limit	`0`	`0`	Passed
control: joint below	`0`	`0`	Passed
control: glide edge	`181500`	`176953`	Failed

SHA-256 / d2419577f3e31f3c700ece6b92a0c656589c852b34a9d52f1d1e42b95dcdac16

2 / The unsuccessful fix

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json
from fractions import Fraction
N = 1
observations = []
def solve(income_tax, joint):
    thr = 1813000 * (2 if joint else 1)
    if income_tax <= thr: return 0
    soli = (income_tax - thr) * Fraction(119, 1000)
    return int(soli)
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
cases = [[('regression glide-base 1', (1900000, False), 10353), ('regression glide-base 2', (3700000, True), 8806),
  ('partial repair guard 1', (5000000, False), 275000), ('partial repair guard 2', (3626001, False), 199430),
  ('control: at limit', (1813000, False), 0), ('control: joint below', (3000000, True), 0),
  ('control: glide edge', (3300000, False), 176953)],
 [('regression glide-base 1', (3300000, False), 176953), ('regression glide-base 2', (1813009, False), 1),
  ('partial repair guard 1', (3835420, False), 210948), ('partial repair guard 2', (3974588, False), 218602),
  ('control: joint glide', (3700000, True), 8806), ('control: joint below', (3000000, True), 0),
  ('control: at limit', (1813000, False), 0), ('control: gliding zone', (1900000, False), 10353)],
 [('regression glide-base 1', (1983210, False), 20254), ('regression glide-base 2', (1813001, False), 0),
  ('partial repair guard 1', (3508965, False), 192993), ('partial repair guard 2', (3491244, False), 192018),
  ('control: at limit', (1813000, False), 0), ('control: gliding zone', (1900000, False), 10353),
  ('control: full rate', (5000000, False), 275000), ('control: joint glide', (3700000, True), 8806)],
 [('regression glide-base 1', (3626001, True), 0), ('regression glide-base 2', (4499538, True), 103951),
  ('partial repair guard 1', (3409571, False), 187526), ('partial repair guard 2', (4398816, False), 241934),
  ('control: joint glide', (3700000, True), 8806), ('control: joint below', (3000000, True), 0),
  ('control: glide edge', (3300000, False), 176953), ('control: at limit', (1813000, False), 0)],
 [('regression glide-base 1', (3256603, False), 171788), ('regression glide-base 2', (2115665, False), 36017),
  ('partial repair guard 1', (5112893, False), 281209), ('partial repair guard 2', (4374325, False), 240587),
  ('control: at limit', (1813000, False), 0), ('control: gliding zone', (1900000, False), 10353),
  ('control: full rate', (5000000, False), 275000), ('control: joint glide', (3700000, True), 8806)]]
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 fixture	Actual	Expected	Outcome
regression glide-base 1	`10353`	`10353`	Passed
regression glide-base 2	`8806`	`8806`	Passed
partial repair guard 1	`379253`	`275000`	Failed
partial repair guard 2	`215747`	`199430`	Failed
control: at limit	`0`	`0`	Passed
control: joint below	`0`	`0`	Passed
control: glide edge	`176953`	`176953`	Passed

SHA-256 / e5faa92e65f925bc7cb926e30f3069ba270db0f8759e70a2e2bfad7012d9097c

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.

Member access is invitation-based. Sign in with your invited account to inspect the repair.

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 2026-09-29T14:47:08.031823+00:00.

Case digest / de4e8da1382f3f08840340a89b4a17a1304276c965547410450c742f933409b9