FA-58314 / Double-entry ledger accounting / Member archive

Straight-line depreciation journal: first charge month · case 04

Mid-month assets start depreciating a month late.

Member previewVariant 4 · 3 implementations · 7 checks per implementation

Case contract

x = {'cost', 'salvage', 'life_months', 'start_month', 'convention': 'full_month'|'mid_month'|'next_month', 'through': last month to post}. Depreciable base = cost - salvage. The first charge month is start_month (start_month + 1 for next_month). Charges use cumulative rounding: target accumulated after the j-th charge month is round(base*j/life) or, for mid_month, round(base*(2j-1)/(2*life)), half-up and capped at base; each month posts target - accumulated. Posting stops after 'through' or once accumulated reaches base. Return {'schedule': [[month, amount]], 'accumulated', 'book_value': cost - accumulated}.

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: first charge month	`{"accumulated": 1500, "book_value": 34500, "schedule": [[2, 500], [3, 1000]]}`	`{"accumulated": 2500, "book_value": 33500, "schedule": [[1, 500], [2, 1000], [3, 1000]]}`	Failed

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