{customerId__c=1, addressId__c=8212BJ154, invoiceType__c=AdvancePayment, invoiceTypeLocalized__c=Voorschot, invoiceDate__c=2015-02-13 00:00:00, paymentDueDate__c=2015-02-20 00:00:00, invoiceNumber__c=157005888, startDate__c=2015-03-01 00:00:00, endDate__c=2015-04-01 00:00:00, periodDescription__c=Maart 2015, amount__c=165.29, vatAmount__c=34.71, totalAmount__c=0.00, Id=a000X000015AAmsOOO}

stringListInvoice = stringListInvoice + JSON.serialize(invMappingNew)+',';