{
  "title": "Sage Sales Invoice Structure",
  "description": "JSON structure documentation for a Sage Accounting sales invoice representing a customer billing record",
  "type": "object",
  "structure": {
    "id": {"type": "string", "description": "Unique invoice identifier (UUID)"},
    "displayed_as": {"type": "string", "description": "Human-readable invoice reference number (e.g., SI-001)"},
    "date": {
      "type": "string",
      "format": "date",
      "description": "Invoice date in YYYY-MM-DD format"
    },
    "due_date": {
      "type": "string",
      "format": "date",
      "description": "Payment due date in YYYY-MM-DD format"
    },
    "contact": {
      "type": "object",
      "description": "Customer contact reference",
      "properties": {
        "id": {"type": "string", "description": "Contact unique identifier"},
        "displayed_as": {"type": "string", "description": "Contact display name"}
      }
    },
    "reference": {"type": "string", "description": "Optional customer or purchase order reference"},
    "status": {
      "type": "string",
      "description": "Invoice status: DRAFT, SUBMITTED, OUTSTANDING, OVERDUE, PAID, VOID"
    },
    "net_amount": {"type": "number", "description": "Invoice subtotal before tax"},
    "tax_amount": {"type": "number", "description": "Total tax applied"},
    "total_amount": {"type": "number", "description": "Total invoice amount including tax"},
    "outstanding_amount": {"type": "number", "description": "Amount remaining unpaid"},
    "currency": {
      "type": "object",
      "description": "Currency for this invoice",
      "properties": {
        "id": {"type": "string", "description": "ISO 4217 currency code (e.g., GBP, USD, EUR)"}
      }
    },
    "invoice_lines": {
      "type": "array",
      "description": "Line items on the invoice",
      "items": {
        "type": "object",
        "properties": {
          "description": {"type": "string", "description": "Line item description"},
          "quantity": {"type": "number", "description": "Quantity of units"},
          "unit_price": {"type": "number", "description": "Price per unit"},
          "net_amount": {"type": "number", "description": "Line item net total"},
          "tax_amount": {"type": "number", "description": "Line item tax total"}
        }
      }
    },
    "created_at": {"type": "string", "format": "date-time", "description": "ISO 8601 creation timestamp"},
    "updated_at": {"type": "string", "format": "date-time", "description": "ISO 8601 last update timestamp"}
  },
  "required": ["id", "date", "contact", "status", "total_amount"]
}