FA-59778 / Subscription proration billing / Member archive

Ratable monthly schedule of a prepaid term: cumulative remainder allocation · case 03

Monthly schedule parts do not add up to the invoiced amount.

Member previewVariant 3 · 3 implementations · 8 checks per implementation

Case contract

Input {amount, start, end (exclusive)}. The amount is spread by days across calendar months. The cumulative amount through each month is floor(amount*cumulative_days/total_days), and each month gets the increase, so the parts sum exactly to amount. Return [["YYYY-MM", cents]] for each month touched.

Why this case matters

Prepaid subscriptions are recognized day-by-day, and per-month rounding must not leak or create cents.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
regression 0	`[["2023-06", 8], ["2023-07", 27], ["2023-08", 27], ["2023-09", 26], ["2023-10", 8]]`	`[["2023-06", 8], ["2023-07", 28], ["2023-08", 28], ["2023-09", 26], ["2023-10", 9]]`	Failed

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