{
  "operation": "CreateInvoice",
  "description": "Create a new invoice for a client in WHMCS.",
  "request": {
    "method": "POST",
    "url": "https://example.com/includes/api.php",
    "headers": {
      "Content-Type": "application/x-www-form-urlencoded"
    },
    "body": {
      "identifier": "your-api-identifier",
      "secret": "your-api-secret",
      "action": "CreateInvoice",
      "responsetype": "json",
      "userid": 1,
      "status": "Unpaid",
      "sendinvoice": true,
      "paymentmethod": "paypal",
      "duedate": "20260601",
      "itemdescription[0]": "Monthly Hosting - May 2026",
      "itemamount[0]": "9.99",
      "itemtaxed[0]": 1
    }
  },
  "response": {
    "status": 200,
    "body": {
      "result": "success",
      "invoiceid": 42
    }
  }
}