diff --git a/Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/services/PaymentManagementService.cpp b/Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/services/PaymentManagementService.cpp
index 45f1742..dfd9aeb 100644
--- a/Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/services/PaymentManagementService.cpp
+++ b/Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/services/PaymentManagementService.cpp
@@ -401,9 +401,9 @@ Description: Provides access to all invoices stored in the data store.
 Parameters:
 	- none
 Returns:
-	- util::Map<std::string, Invoice*>&: Map of invoice IDs to invoice objects
+	- util::Map<std::string, Invoice*>: Map of invoice IDs to invoice objects
 */
-util::Map<std::string, Invoice*>& PaymentManagementService::getAllInvoices()
+util::Map<std::string, Invoice*> PaymentManagementService::getAllInvoices()
 {
 	DataStoreLockGuard lock(m_dataStore);
 	util::Map<std::string, Invoice*> invoices;
diff --git a/Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/services/PaymentManagementService.h b/Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/services/PaymentManagementService.h
index 8961a2d..04c5560 100644
--- a/Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/services/PaymentManagementService.h
+++ b/Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/services/PaymentManagementService.h
@@ -28,7 +28,7 @@ public:
     void generateInvoice(ServiceBooking* booking);
     util::Map<std::string, Invoice*> getInvoices(const std::string& customerID);
     void completePayment(const std::string& invoiceID, util::PaymentMode paymentMode);
-    util::Map<std::string, Invoice*>& getAllInvoices();
+    util::Map<std::string, Invoice*> getAllInvoices();
     void confirmPayment(const std::string& invoiceID);
     void sendPaymentReminders();
     void sendNotification(User* user, const std::string& title, const std::string& message) override;