Issue a draft — this is the booking step (accountant role).

In one transaction it assigns the next invoice number, posts the journal entry (debit the AR control account, credit revenue per line, credit output VAT per VAT code), opens the receivable open item the customer's payment will settle, freezes the invoice against further edits (status → issued) and renders the PDF+QR snapshot. The turnover reaches the VAT return from here — a draft never does.

Only a draft can be issued: re-issuing an issued invoice is a 409. It is also refused when the invoice is not ready (no customer, no lines, a line without a revenue account…) — call GET …/ar/invoices/{invoice_id}/readiness first, whose blocking list is exactly what this refuses on — when the issue_date is not inside an open accounting period, or when the fiscal year has no AR control account configured.

Returns the issued invoice (now with document_no and commercial_document_id). A renderer outage does not fail the issue: the booking stands and the snapshot stays pending, re-rendered on demand by GET …/ar/invoices/{invoice_id}/pdf. To undo one, reverse its journal entry; there is no un-issue.