FA-58130 / Double-entry ledger accounting / Member archive

Aging-based allowance adjustment: write-off allowance sign · case 05

Writing off a bad debt increases the allowance and shrinks the period adjustment.

Member previewVariant 5 · 3 implementations · 7 checks per implementation

Case contract

x = {'as_of': day, 'invoices': [[id, due_day, open cents]], 'rates': [[max_days_past_due or None, basis points]] ascending, 'allowance': existing credit balance (negative = debit balance), 'writeoffs': ids}. Written-off invoices leave receivables and reduce the allowance by their amount. Days past due = max(0, as_of - due); an invoice goes in the first bucket whose limit is None or >= days. Required allowance = sum over buckets of bucket total * bp / 10000 rounded half-up per bucket. Return {'buckets', 'required', 'adjustment': required - allowance after write-offs, 'net_ar'}.

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.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
regression: write-off allowance sign	`{"adjustment": -1919, "buckets": [4000, 4005, 0], "net_ar": 7424, "required": 581}`	`{"adjustment": 3081, "buckets": [4000, 4005, 0], "net_ar": 7424, "required": 581}`	Failed

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