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FA-58191 / Double-entry ledger accounting / Open access

VAT invoice journal: inclusive net derivation · case 01

Inclusive sales book the full gross as revenue while also booking tax.

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ROOT CAUSE

The inclusive net is not reduced by the extracted tax.

THE FAILURE

The inclusive net is not reduced by the extracted tax.

Unsuccessful approach: Grossing down separately rounds independently, so net plus tax can miss the receivable by a cent.

Case contract

x = {'mode': 'inclusive'|'exclusive', 'rounding': 'line'|'invoice', 'lines': [[amount, rate_bp, account]]}. Exclusive: tax = amount*bp/10000. Inclusive: tax = amount*bp/(10000+bp). Rounding is half-up to the cent, per line ('line', summed per rate) or once per rate on the summed amounts ('invoice'). Tax is keyed by str(rate_bp). Inclusive: receivable = sum amounts, net = receivable - total tax. Exclusive: net = sum amounts, receivable = net + total tax. Return {'receivable', 'net', 'tax'}.

Why this case matters

Ledger software must keep debits equal to credits and apply normal-balance, period and cutoff rules exactly; small sign or boundary slips silently misstate financial statements.

1 / The failure

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

N = 1
observations = []
def solve(x):
    def rnd(n, d):
        q, r = divmod(n, d)
        return q + (1 if 2 * r >= d else 0)
    incl = x['mode'] == 'inclusive'
    groups = {}
    tax = {}
    for amount, bp, acct in x['lines']:
        denom = 10000 + bp if incl else 10000
        key = str(bp)
        if x['rounding'] == 'line':
            tax[key] = tax.get(key, 0) + rnd(amount * bp, denom)
        groups[key] = groups.get(key, 0) + amount
    if x['rounding'] == 'invoice':
        for key, total in groups.items():
            bp = int(key)
            tax[key] = rnd(total * bp, 10000 + bp if incl else 10000)
    gross_in = sum(groups.values())
    total_tax = sum(tax.values())
    if incl:
        receivable = gross_in
        net = gross_in
    else:
        receivable = gross_in + total_tax
        net = gross_in
    return {'receivable': receivable, 'net': net, 'tax': tax}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['regression: inclusive net derivation', {'mode': 'inclusive', 'rounding': 'invoice', 'lines': [[1999, 2100, 'services'], [12345, 2100, 'sales'], [2500, 500, 'services'], [105, 2100, 'services']]}, {'receivable': 16949, 'net': 14322, 'tax': {'2100': 2508, '500': 119}}], ['regression: inclusive net derivation, partial-repair probe', {'mode': 'inclusive', 'rounding': 'invoice', 'lines': [[15, 1900, 'services'], [15, 2000, 'services'], [15, 0, 'sales'], [1000, 2100, 'services'], [15, 500, 'sales']]}, {'receivable': 1060, 'net': 880, 'tax': {'1900': 2, '2000': 3, '0': 0, '2100': 174, '500': 1}}], ['control 1', {'mode': 'exclusive', 'rounding': 'line', 'lines': [[2500, 1900, 'sales'], [15, 700, 'sales']]}, {'receivable': 2991, 'net': 2515, 'tax': {'1900': 475, '700': 1}}], ['control 2', {'mode': 'exclusive', 'rounding': 'line', 'lines': [[105, 700, 'services'], [5, 700, 'sales'], [5, 500, 'services'], [105, 1900, 'services'], [15, 500, 'services']]}, {'receivable': 263, 'net': 235, 'tax': {'700': 7, '500': 1, '1900': 20}}], ['control 3', {'mode': 'exclusive', 'rounding': 'line', 'lines': [[1999, 700, 'services'], [999, 0, 'sales']]}, {'receivable': 3138, 'net': 2998, 'tax': {'700': 140, '0': 0}}], ['control 4', {'mode': 'exclusive', 'rounding': 'invoice', 'lines': [[1000, 2100, 'services'], [999, 2000, 'sales'], [999, 0, 'sales'], [1999, 2100, 'services'], [1000, 2000, 'services']]}, {'receivable': 7027, 'net': 5997, 'tax': {'2100': 630, '2000': 400, '0': 0}}], ['control 5', {'mode': 'exclusive', 'rounding': 'line', 'lines': [[1000, 2100, 'sales'], [999, 1900, 'sales'], [999, 0, 'services'], [2500, 500, 'services'], [15, 700, 'sales']]}, {'receivable': 6039, 'net': 5513, 'tax': {'2100': 210, '1900': 190, '0': 0, '500': 125, '700': 1}}]], [['regression: inclusive net derivation', {'mode': 'inclusive', 'rounding': 'invoice', 'lines': [[999, 500, 'services'], [15, 700, 'sales']]}, {'receivable': 1014, 'net': 965, 'tax': {'500': 48, '700': 1}}], ['regression: inclusive net derivation, partial-repair probe', {'mode': 'inclusive', 'rounding': 'line', 'lines': [[15, 2100, 'services'], [5, 2000, 'sales'], [12345, 2000, 'sales']]}, {'receivable': 12365, 'net': 10303, 'tax': {'2100': 3, '2000': 2059}}], ['control 1', {'mode': 'exclusive', 'rounding': 'invoice', 'lines': [[15, 1900, 'services']]}, {'receivable': 18, 'net': 15, 'tax': {'1900': 3}}], ['control 2', {'mode': 'exclusive', 'rounding': 'invoice', 'lines': [[12345, 700, 'sales'], [15, 2100, 'sales'], [1000, 700, 'sales'], [2500, 0, 'services']]}, {'receivable': 16797, 'net': 15860, 'tax': {'700': 934, '2100': 3, '0': 0}}], ['control 3', {'mode': 'inclusive', 'rounding': 'line', 'lines': [[1999, 0, 'sales']]}, {'receivable': 1999, 'net': 1999, 'tax': {'0': 0}}], ['control 4', {'mode': 'exclusive', 'rounding': 'invoice', 'lines': [[5, 1900, 'services'], [5, 2000, 'sales']]}, {'receivable': 12, 'net': 10, 'tax': {'1900': 1, '2000': 1}}], ['control 5', {'mode': 'exclusive', 'rounding': 'invoice', 'lines': [[1000, 0, 'sales'], [1000, 2100, 'services'], [2500, 2000, 'sales'], [15, 2000, 'sales']]}, {'receivable': 5228, 'net': 4515, 'tax': {'0': 0, '2100': 210, '2000': 503}}]], [['regression: inclusive net derivation', {'mode': 'inclusive', 'rounding': 'invoice', 'lines': [[12345, 700, 'sales'], [105, 700, 'sales']]}, {'receivable': 12450, 'net': 11636, 'tax': {'700': 814}}], ['regression: inclusive net derivation, partial-repair probe', {'mode': 'inclusive', 'rounding': 'invoice', 'lines': [[1999, 2100, 'sales'], [105, 2000, 'sales'], [2500, 0, 'services']]}, {'receivable': 4604, 'net': 4239, 'tax': {'2100': 347, '2000': 18, '0': 0}}], ['control 1', {'mode': 'exclusive', 'rounding': 'line', 'lines': [[1999, 2100, 'sales'], [5, 2100, 'sales'], [12345, 0, 'services'], [2500, 2000, 'sales']]}, {'receivable': 17770, 'net': 16849, 'tax': {'2100': 421, '0': 0, '2000': 500}}], ['control 2', {'mode': 'exclusive', 'rounding': 'line', 'lines': [[5, 700, 'sales'], [1000, 1900, 'sales'], [15, 2000, 'services'], [1999, 700, 'services'], [15, 0, 'services']]}, {'receivable': 3367, 'net': 3034, 'tax': {'700': 140, '1900': 190, '2000': 3, '0': 0}}], ['control 3', {'mode': 'exclusive', 'rounding': 'invoice', 'lines': [[1999, 2000, 'sales'], [1999, 1900, 'sales']]}, {'receivable': 4778, 'net': 3998, 'tax': {'2000': 400, '1900': 380}}], ['control 4', {'mode': 'inclusive', 'rounding': 'invoice', 'lines': [[999, 0, 'sales']]}, {'receivable': 999, 'net': 999, 'tax': {'0': 0}}], ['control 5', {'mode': 'exclusive', 'rounding': 'invoice', 'lines': [[12345, 2100, 'sales'], [1000, 2100, 'services']]}, {'receivable': 16147, 'net': 13345, 'tax': {'2100': 2802}}]], [['regression: inclusive net derivation', {'mode': 'inclusive', 'rounding': 'invoice', 'lines': [[15, 2100, 'sales'], [15, 2100, 'sales'], [105, 0, 'sales'], [1999, 1900, 'sales']]}, {'receivable': 2134, 'net': 1810, 'tax': {'2100': 5, '0': 0, '1900': 319}}], ['regression: inclusive net derivation, partial-repair probe', {'mode': 'inclusive', 'rounding': 'line', 'lines': [[105, 2100, 'sales'], [999, 2000, 'sales'], [105, 2000, 'sales']]}, {'receivable': 1209, 'net': 1006, 'tax': {'2100': 18, '2000': 185}}], ['control 1', {'mode': 'exclusive', 'rounding': 'invoice', 'lines': [[15, 1900, 'sales'], [2500, 1900, 'services'], [15, 700, 'sales']]}, {'receivable': 3009, 'net': 2530, 'tax': {'1900': 478, '700': 1}}], ['control 2', {'mode': 'exclusive', 'rounding': 'invoice', 'lines': [[105, 700, 'services'], [1000, 700, 'sales'], [5, 2100, 'services'], [105, 700, 'services'], [105, 2000, 'services']]}, {'receivable': 1427, 'net': 1320, 'tax': {'700': 85, '2100': 1, '2000': 21}}], ['control 3', {'mode': 'exclusive', 'rounding': 'invoice', 'lines': [[105, 700, 'services'], [15, 0, 'services'], [1999, 0, 'sales'], [1999, 700, 'services'], [15, 1900, 'sales']]}, {'receivable': 4283, 'net': 4133, 'tax': {'700': 147, '0': 0, '1900': 3}}], ['control 4', {'mode': 'exclusive', 'rounding': 'line', 'lines': [[1000, 0, 'sales']]}, {'receivable': 1000, 'net': 1000, 'tax': {'0': 0}}], ['control 5', {'mode': 'exclusive', 'rounding': 'line', 'lines': [[12345, 2100, 'sales'], [1000, 700, 'sales'], [15, 1900, 'services'], [105, 2000, 'sales'], [1999, 2100, 'services']]}, {'receivable': 18570, 'net': 15464, 'tax': {'2100': 3012, '700': 70, '1900': 3, '2000': 21}}]], [['regression: inclusive net derivation', {'mode': 'inclusive', 'rounding': 'line', 'lines': [[15, 0, 'sales'], [1999, 0, 'services'], [999, 700, 'services'], [15, 500, 'sales'], [999, 2100, 'sales']]}, {'receivable': 4027, 'net': 3788, 'tax': {'0': 0, '700': 65, '500': 1, '2100': 173}}], ['regression: inclusive net derivation, partial-repair probe', {'mode': 'inclusive', 'rounding': 'line', 'lines': [[105, 2100, 'sales'], [1000, 2000, 'sales'], [1999, 500, 'sales'], [12345, 2000, 'services'], [1000, 500, 'sales']]}, {'receivable': 16449, 'net': 14063, 'tax': {'2100': 18, '2000': 2225, '500': 143}}], ['control 1', {'mode': 'exclusive', 'rounding': 'invoice', 'lines': [[15, 500, 'sales']]}, {'receivable': 16, 'net': 15, 'tax': {'500': 1}}], ['control 2', {'mode': 'exclusive', 'rounding': 'invoice', 'lines': [[999, 700, 'services']]}, {'receivable': 1069, 'net': 999, 'tax': {'700': 70}}], ['control 3', {'mode': 'exclusive', 'rounding': 'invoice', 'lines': [[105, 1900, 'sales'], [12345, 500, 'sales'], [1000, 2000, 'sales'], [999, 700, 'services']]}, {'receivable': 15356, 'net': 14449, 'tax': {'1900': 20, '500': 617, '2000': 200, '700': 70}}], ['control 4', {'mode': 'exclusive', 'rounding': 'invoice', 'lines': [[5, 2000, 'sales'], [5, 700, 'services'], [12345, 500, 'services'], [105, 1900, 'sales']]}, {'receivable': 13098, 'net': 12460, 'tax': {'2000': 1, '700': 0, '500': 617, '1900': 20}}], ['control 5', {'mode': 'exclusive', 'rounding': 'line', 'lines': [[2500, 700, 'services'], [105, 0, 'sales'], [5, 1900, 'services']]}, {'receivable': 2786, 'net': 2610, 'tax': {'700': 175, '0': 0, '1900': 1}}]]]
for label, args, expected in fixtures[N-1]:
    try:
        actual = solve(args)
    except Exception as exc:
        actual = 'raised ' + type(exc).__name__
    check(label, actual, 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: inclusive net derivation{'net': 16949, 'receivable': 16949, 'tax': {'2100': 2508, '500': 119}}{'net': 14322, 'receivable': 16949, 'tax': {'2100': 2508, '500': 119}}Failed
regression: inclusive net derivation, partial-repair probe{'net': 1060, 'receivable': 1060, 'tax': {'0': 0, '1900': 2, '2000': 3, '2100': 174, '500': 1}}{'net': 880, 'receivable': 1060, 'tax': {'0': 0, '1900': 2, '2000': 3, '2100': 174, '500': 1}}Failed
control 1{'net': 2515, 'receivable': 2991, 'tax': {'1900': 475, '700': 1}}{'net': 2515, 'receivable': 2991, 'tax': {'1900': 475, '700': 1}}Passed
control 2{'net': 235, 'receivable': 263, 'tax': {'1900': 20, '500': 1, '700': 7}}{'net': 235, 'receivable': 263, 'tax': {'1900': 20, '500': 1, '700': 7}}Passed
control 3{'net': 2998, 'receivable': 3138, 'tax': {'0': 0, '700': 140}}{'net': 2998, 'receivable': 3138, 'tax': {'0': 0, '700': 140}}Passed
control 4{'net': 5997, 'receivable': 7027, 'tax': {'0': 0, '2000': 400, '2100': 630}}{'net': 5997, 'receivable': 7027, 'tax': {'0': 0, '2000': 400, '2100': 630}}Passed
control 5{'net': 5513, 'receivable': 6039, 'tax': {'0': 0, '1900': 190, '2100': 210, '500': 125, '700': 1}}{'net': 5513, 'receivable': 6039, 'tax': {'0': 0, '1900': 190, '2100': 210, '500': 125, '700': 1}}Passed

SHA-256 / 118be6ef4ddf848e633ccd4e43482cfca6064f9e9e40656258baa19c4ba4fd1d

2 / The unsuccessful fix

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

N = 1
observations = []
def solve(x):
    def rnd(n, d):
        q, r = divmod(n, d)
        return q + (1 if 2 * r >= d else 0)
    incl = x['mode'] == 'inclusive'
    groups = {}
    tax = {}
    for amount, bp, acct in x['lines']:
        denom = 10000 + bp if incl else 10000
        key = str(bp)
        if x['rounding'] == 'line':
            tax[key] = tax.get(key, 0) + rnd(amount * bp, denom)
        groups[key] = groups.get(key, 0) + amount
    if x['rounding'] == 'invoice':
        for key, total in groups.items():
            bp = int(key)
            tax[key] = rnd(total * bp, 10000 + bp if incl else 10000)
    gross_in = sum(groups.values())
    total_tax = sum(tax.values())
    if incl:
        receivable = gross_in
        net = sum(rnd(v * 10000, 10000 + int(k)) for k, v in groups.items())
    else:
        receivable = gross_in + total_tax
        net = gross_in
    return {'receivable': receivable, 'net': net, 'tax': tax}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['regression: inclusive net derivation', {'mode': 'inclusive', 'rounding': 'invoice', 'lines': [[1999, 2100, 'services'], [12345, 2100, 'sales'], [2500, 500, 'services'], [105, 2100, 'services']]}, {'receivable': 16949, 'net': 14322, 'tax': {'2100': 2508, '500': 119}}], ['regression: inclusive net derivation, partial-repair probe', {'mode': 'inclusive', 'rounding': 'invoice', 'lines': [[15, 1900, 'services'], [15, 2000, 'services'], [15, 0, 'sales'], [1000, 2100, 'services'], [15, 500, 'sales']]}, {'receivable': 1060, 'net': 880, 'tax': {'1900': 2, '2000': 3, '0': 0, '2100': 174, '500': 1}}], ['control 1', {'mode': 'exclusive', 'rounding': 'line', 'lines': [[2500, 1900, 'sales'], [15, 700, 'sales']]}, {'receivable': 2991, 'net': 2515, 'tax': {'1900': 475, '700': 1}}], ['control 2', {'mode': 'exclusive', 'rounding': 'line', 'lines': [[105, 700, 'services'], [5, 700, 'sales'], [5, 500, 'services'], [105, 1900, 'services'], [15, 500, 'services']]}, {'receivable': 263, 'net': 235, 'tax': {'700': 7, '500': 1, '1900': 20}}], ['control 3', {'mode': 'exclusive', 'rounding': 'line', 'lines': [[1999, 700, 'services'], [999, 0, 'sales']]}, {'receivable': 3138, 'net': 2998, 'tax': {'700': 140, '0': 0}}], ['control 4', {'mode': 'exclusive', 'rounding': 'invoice', 'lines': [[1000, 2100, 'services'], [999, 2000, 'sales'], [999, 0, 'sales'], [1999, 2100, 'services'], [1000, 2000, 'services']]}, {'receivable': 7027, 'net': 5997, 'tax': {'2100': 630, '2000': 400, '0': 0}}], ['control 5', {'mode': 'exclusive', 'rounding': 'line', 'lines': [[1000, 2100, 'sales'], [999, 1900, 'sales'], [999, 0, 'services'], [2500, 500, 'services'], [15, 700, 'sales']]}, {'receivable': 6039, 'net': 5513, 'tax': {'2100': 210, '1900': 190, '0': 0, '500': 125, '700': 1}}]], [['regression: inclusive net derivation', {'mode': 'inclusive', 'rounding': 'invoice', 'lines': [[999, 500, 'services'], [15, 700, 'sales']]}, {'receivable': 1014, 'net': 965, 'tax': {'500': 48, '700': 1}}], ['regression: inclusive net derivation, partial-repair probe', {'mode': 'inclusive', 'rounding': 'line', 'lines': [[15, 2100, 'services'], [5, 2000, 'sales'], [12345, 2000, 'sales']]}, {'receivable': 12365, 'net': 10303, 'tax': {'2100': 3, '2000': 2059}}], ['control 1', {'mode': 'exclusive', 'rounding': 'invoice', 'lines': [[15, 1900, 'services']]}, {'receivable': 18, 'net': 15, 'tax': {'1900': 3}}], ['control 2', {'mode': 'exclusive', 'rounding': 'invoice', 'lines': [[12345, 700, 'sales'], [15, 2100, 'sales'], [1000, 700, 'sales'], [2500, 0, 'services']]}, {'receivable': 16797, 'net': 15860, 'tax': {'700': 934, '2100': 3, '0': 0}}], ['control 3', {'mode': 'inclusive', 'rounding': 'line', 'lines': [[1999, 0, 'sales']]}, {'receivable': 1999, 'net': 1999, 'tax': {'0': 0}}], ['control 4', {'mode': 'exclusive', 'rounding': 'invoice', 'lines': [[5, 1900, 'services'], [5, 2000, 'sales']]}, {'receivable': 12, 'net': 10, 'tax': {'1900': 1, '2000': 1}}], ['control 5', {'mode': 'exclusive', 'rounding': 'invoice', 'lines': [[1000, 0, 'sales'], [1000, 2100, 'services'], [2500, 2000, 'sales'], [15, 2000, 'sales']]}, {'receivable': 5228, 'net': 4515, 'tax': {'0': 0, '2100': 210, '2000': 503}}]], [['regression: inclusive net derivation', {'mode': 'inclusive', 'rounding': 'invoice', 'lines': [[12345, 700, 'sales'], [105, 700, 'sales']]}, {'receivable': 12450, 'net': 11636, 'tax': {'700': 814}}], ['regression: inclusive net derivation, partial-repair probe', {'mode': 'inclusive', 'rounding': 'invoice', 'lines': [[1999, 2100, 'sales'], [105, 2000, 'sales'], [2500, 0, 'services']]}, {'receivable': 4604, 'net': 4239, 'tax': {'2100': 347, '2000': 18, '0': 0}}], ['control 1', {'mode': 'exclusive', 'rounding': 'line', 'lines': [[1999, 2100, 'sales'], [5, 2100, 'sales'], [12345, 0, 'services'], [2500, 2000, 'sales']]}, {'receivable': 17770, 'net': 16849, 'tax': {'2100': 421, '0': 0, '2000': 500}}], ['control 2', {'mode': 'exclusive', 'rounding': 'line', 'lines': [[5, 700, 'sales'], [1000, 1900, 'sales'], [15, 2000, 'services'], [1999, 700, 'services'], [15, 0, 'services']]}, {'receivable': 3367, 'net': 3034, 'tax': {'700': 140, '1900': 190, '2000': 3, '0': 0}}], ['control 3', {'mode': 'exclusive', 'rounding': 'invoice', 'lines': [[1999, 2000, 'sales'], [1999, 1900, 'sales']]}, {'receivable': 4778, 'net': 3998, 'tax': {'2000': 400, '1900': 380}}], ['control 4', {'mode': 'inclusive', 'rounding': 'invoice', 'lines': [[999, 0, 'sales']]}, {'receivable': 999, 'net': 999, 'tax': {'0': 0}}], ['control 5', {'mode': 'exclusive', 'rounding': 'invoice', 'lines': [[12345, 2100, 'sales'], [1000, 2100, 'services']]}, {'receivable': 16147, 'net': 13345, 'tax': {'2100': 2802}}]], [['regression: inclusive net derivation', {'mode': 'inclusive', 'rounding': 'invoice', 'lines': [[15, 2100, 'sales'], [15, 2100, 'sales'], [105, 0, 'sales'], [1999, 1900, 'sales']]}, {'receivable': 2134, 'net': 1810, 'tax': {'2100': 5, '0': 0, '1900': 319}}], ['regression: inclusive net derivation, partial-repair probe', {'mode': 'inclusive', 'rounding': 'line', 'lines': [[105, 2100, 'sales'], [999, 2000, 'sales'], [105, 2000, 'sales']]}, {'receivable': 1209, 'net': 1006, 'tax': {'2100': 18, '2000': 185}}], ['control 1', {'mode': 'exclusive', 'rounding': 'invoice', 'lines': [[15, 1900, 'sales'], [2500, 1900, 'services'], [15, 700, 'sales']]}, {'receivable': 3009, 'net': 2530, 'tax': {'1900': 478, '700': 1}}], ['control 2', {'mode': 'exclusive', 'rounding': 'invoice', 'lines': [[105, 700, 'services'], [1000, 700, 'sales'], [5, 2100, 'services'], [105, 700, 'services'], [105, 2000, 'services']]}, {'receivable': 1427, 'net': 1320, 'tax': {'700': 85, '2100': 1, '2000': 21}}], ['control 3', {'mode': 'exclusive', 'rounding': 'invoice', 'lines': [[105, 700, 'services'], [15, 0, 'services'], [1999, 0, 'sales'], [1999, 700, 'services'], [15, 1900, 'sales']]}, {'receivable': 4283, 'net': 4133, 'tax': {'700': 147, '0': 0, '1900': 3}}], ['control 4', {'mode': 'exclusive', 'rounding': 'line', 'lines': [[1000, 0, 'sales']]}, {'receivable': 1000, 'net': 1000, 'tax': {'0': 0}}], ['control 5', {'mode': 'exclusive', 'rounding': 'line', 'lines': [[12345, 2100, 'sales'], [1000, 700, 'sales'], [15, 1900, 'services'], [105, 2000, 'sales'], [1999, 2100, 'services']]}, {'receivable': 18570, 'net': 15464, 'tax': {'2100': 3012, '700': 70, '1900': 3, '2000': 21}}]], [['regression: inclusive net derivation', {'mode': 'inclusive', 'rounding': 'line', 'lines': [[15, 0, 'sales'], [1999, 0, 'services'], [999, 700, 'services'], [15, 500, 'sales'], [999, 2100, 'sales']]}, {'receivable': 4027, 'net': 3788, 'tax': {'0': 0, '700': 65, '500': 1, '2100': 173}}], ['regression: inclusive net derivation, partial-repair probe', {'mode': 'inclusive', 'rounding': 'line', 'lines': [[105, 2100, 'sales'], [1000, 2000, 'sales'], [1999, 500, 'sales'], [12345, 2000, 'services'], [1000, 500, 'sales']]}, {'receivable': 16449, 'net': 14063, 'tax': {'2100': 18, '2000': 2225, '500': 143}}], ['control 1', {'mode': 'exclusive', 'rounding': 'invoice', 'lines': [[15, 500, 'sales']]}, {'receivable': 16, 'net': 15, 'tax': {'500': 1}}], ['control 2', {'mode': 'exclusive', 'rounding': 'invoice', 'lines': [[999, 700, 'services']]}, {'receivable': 1069, 'net': 999, 'tax': {'700': 70}}], ['control 3', {'mode': 'exclusive', 'rounding': 'invoice', 'lines': [[105, 1900, 'sales'], [12345, 500, 'sales'], [1000, 2000, 'sales'], [999, 700, 'services']]}, {'receivable': 15356, 'net': 14449, 'tax': {'1900': 20, '500': 617, '2000': 200, '700': 70}}], ['control 4', {'mode': 'exclusive', 'rounding': 'invoice', 'lines': [[5, 2000, 'sales'], [5, 700, 'services'], [12345, 500, 'services'], [105, 1900, 'sales']]}, {'receivable': 13098, 'net': 12460, 'tax': {'2000': 1, '700': 0, '500': 617, '1900': 20}}], ['control 5', {'mode': 'exclusive', 'rounding': 'line', 'lines': [[2500, 700, 'services'], [105, 0, 'sales'], [5, 1900, 'services']]}, {'receivable': 2786, 'net': 2610, 'tax': {'700': 175, '0': 0, '1900': 1}}]]]
for label, args, expected in fixtures[N-1]:
    try:
        actual = solve(args)
    except Exception as exc:
        actual = 'raised ' + type(exc).__name__
    check(label, actual, 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: inclusive net derivation{'net': 14322, 'receivable': 16949, 'tax': {'2100': 2508, '500': 119}}{'net': 14322, 'receivable': 16949, 'tax': {'2100': 2508, '500': 119}}Passed
regression: inclusive net derivation, partial-repair probe{'net': 881, 'receivable': 1060, 'tax': {'0': 0, '1900': 2, '2000': 3, '2100': 174, '500': 1}}{'net': 880, 'receivable': 1060, 'tax': {'0': 0, '1900': 2, '2000': 3, '2100': 174, '500': 1}}Failed
control 1{'net': 2515, 'receivable': 2991, 'tax': {'1900': 475, '700': 1}}{'net': 2515, 'receivable': 2991, 'tax': {'1900': 475, '700': 1}}Passed
control 2{'net': 235, 'receivable': 263, 'tax': {'1900': 20, '500': 1, '700': 7}}{'net': 235, 'receivable': 263, 'tax': {'1900': 20, '500': 1, '700': 7}}Passed
control 3{'net': 2998, 'receivable': 3138, 'tax': {'0': 0, '700': 140}}{'net': 2998, 'receivable': 3138, 'tax': {'0': 0, '700': 140}}Passed
control 4{'net': 5997, 'receivable': 7027, 'tax': {'0': 0, '2000': 400, '2100': 630}}{'net': 5997, 'receivable': 7027, 'tax': {'0': 0, '2000': 400, '2100': 630}}Passed
control 5{'net': 5513, 'receivable': 6039, 'tax': {'0': 0, '1900': 190, '2100': 210, '500': 125, '700': 1}}{'net': 5513, 'receivable': 6039, 'tax': {'0': 0, '1900': 190, '2100': 210, '500': 125, '700': 1}}Passed

SHA-256 / 4256467faf41ee8510b52ff546f6c50fba37e72aa4d8afb4bd7b89fd77fa92b2

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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.

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Verification & scope

A deterministic bounded teaching model with stipulated toy bookkeeping rules stated in the contract; amounts are integer cents; it makes no claim of conformance to any accounting standard or product. 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 2026-09-29T14:46:24.285810+00:00.

Case digest / f4b623e019c511594c27038ce7129651a752ca86f14c375b91b1832681183f6f