Expand a group code (kit) onto the estimate as individual line items. Each component line is tagged with the originating GroupCodeId; any price rules attached to the kit are applied during the resulting recalculation.

"us-sales-tax" or "vat" — snapshot at estimate creation.

Set when this invoice was merged into a new combined invoice (it is then Superseded): the id of the successor bill.

Human-readable number of the successor combined invoice this one was merged into (set only on a Superseded source). Lets the UI link forward without a second fetch.

When the bill was issued (Draft → Unpaid) and its totals frozen. Null for Drafts and legacy invoices issued before the issue boundary.