One authored outgoing invoice with its lines (CompanyMember read).

Carries the header (customer, dates, currency, discounts), every line with its computed net_amount/vat_amount/gross_amount, the document totals, and the lifecycle: status (draft → issued → cancelled), document_no (assigned at issue — null on a draft), commercial_document_id / snapshot_document_id (the booked document and the frozen PDF), plus the derived payment_status and open_amount read from the linked open item.

This is the authored arm only. A receivable that arrived as an ingested document is an item, not an ar_invoice; the two arms are listed together by GET …/ar/receivables. Use GET …/ar/invoices/{invoice_id}/related for the journal entry, the settling bank transactions and the credit-note chain.