Stores the date after which the invoice is no longer payable, on a draft or an open invoice. Calling it again moves the date. Once the date passes, an open invoice is voided: its payment link stops working and the hosted page shows it as void. A draft whose date has passed cannot be sent until the date is moved or removed. Rejects a date that is not in the future (400); a paid or void invoice, an invoice a subscription manages, or a date at or before the scheduled send date (422); and a disabled environment (503).