Lightspark Periodic Statements API

Build, deliver, and evidence a Regulation E periodic statement for a customer's internal account. A statement period is a calendar month in US Central time (`America/Chicago`). A statement is issued for each customer's own USD internal account and covers their whole balance. Money received through a rule-based account appears on its owner's statement; rule-based, bulk settlement and platform-owned accounts have no statement of their own. **1. The statement — `GET /internal-accounts/{id}/balance-changes?startDate=&endDate=`** One row per change to the balance, in the order the money moved, with the opening and closing balances for the window in the same response. Page until `hasMore` is false, then assert this identity across every page before you render anything: ``` openingBalance + Σ(data[].amount) == closingBalance ``` If it does not hold, do not send the statement; contact support instead. `startDate` and `endDate` bound a half-open window `[startDate, endDate)`: for a monthly statement, pass the first instant of the month and the first instant of the following month, both in US Central time (for August 2026, `2026-08-01T00:00:00-05:00` and `2026-09-01T00:00:00-05:00`). Grid records a statement as fetched only for a window that is exactly one such month. **2. The receipt — `POST /internal-accounts/{id}/confirm-statement`** Once a month, after you have pulled and issued a period's statement, send a receipt with the `statementMonth` it covers. Grid stores it as the delivery record for that account and period. Sending it again is harmless: the first receipt's time is kept. **Timing** A window whose card settlement has not closed is refused with `409 NOT_YET_AVAILABLE` rather than answered with figures that could still change; retry once it has settled.