Bills: one per charge per payer, with their status, why one is invalid, and their way through the ERP. status is…

Bills: one per charge per payer, with their status, why one is invalid, and their way through the ERP. status is PENDING_VALIDATION for the moment between a bill being written and checked, VALID or INVALID until it is sent, then SENT_TO_ERP, CLOSED_IN_ERP (accepted there) or REJECTED_BY_ERP, or WAIVED; a rejected bill is checked again with the rest and goes back to VALID or INVALID. system_comment says why an invalid bill failed its checks, every reason at once, or why the ERP rejected one, and invalid_codes names each failed criterion: C1 to C5 the ERP’s own, R1 to R3 a missing price, task or active task. bill_number is the Billing ID, numbered under the booking or direct checkout it bills (BK-2026-00733-0001) and never changed or reused. source says which of the two it was, or STOCK for a part drawn from a store, and source_number is that booking’s or checkout’s number.