// Create a Map to store all the data of a Invoice
List<Object> invoiceList = new List<Object>();
Map<String, Object> invoiceMap = new Map<String, Object>();
invoiceMap.put('Id', '13');
invoiceMap.put('SyncToken','2');
invoiceMap.put('CustomerRef',new Map<String, Object>{'value' => '9'});
// Initializing the Invoice Line Items
List<Object> lineItemList = new List<Object>();
Map<String, Object> lineItemMap = new Map<String, Object>();
lineItemMap.put('LineNum',1);
lineItemMap.put('Amount',100);
lineItemMap.put('Description','Description Updated');
lineItemMap.put('DetailType', 'SalesItemLineDetail');
Map<String, Object> salesLineItemDetailMap = new Map<String, Object>();
salesLineItemDetailMap.put('Qty',2);
salesLineItemDetailMap.put('UnitPrice',50);
salesLineItemDetailMap.put('TaxCodeRef' , new Map<String, Object>{'value' => 'TAX'});
lineItemMap.put('SalesItemLineDetail', salesLineItemDetailMap);
lineItemList.add(lineItemMap);
// Adding the Line Items to Invoice
invoiceMap.put('Line',lineItemList);
invoiceList.add(invoiceMap);
// Initializing the RequestJSON Data to be passed.
Map<String, Object> reqJSONMap = new Map<String, Object>();
reqJSONMap.put('invoices' , invoiceList);
String reqJSON = JSON.serialize(reqJSONMap);
Map<String, Object> finalReqMap = new Map<String, Object>();
Map<String, Object> reqOptions = new Map<String, Object>();
finalReqMap.put('options' , reqOptions);
finalReqMap.put('version' , '1.0');
finalReqMap.put('action' , 'updateinvoice');
finalReqMap.put('RequestJSON' , reqJSON);
finalReqMap.put('skipDML' , false);
//Required, if QuickBooks Multi-Org is enabled in Breadwinner.
finalReqMap.put('qbOrgId', '!aa00TM');
System.debug('Request ::: ' + finalReqMap);
// Placing a request to Breadwinner Global API
Map<String, Object> respMap = breadwinner_qbo.BreadwinnerQBAPI.call(finalReqMap);
System.debug('Response ::: ' + respMap);