diff --git a/data/filehandler.h b/data/filehandler.h
index 6fd6019..c9bb097 100644
--- a/data/filehandler.h
+++ b/data/filehandler.h
@@ -3,7 +3,7 @@
 
 #include <QVariant>
 
-typedef QHash<int, QVariant> ModelItemValues;
+typedef QMap<int, QVariant> ModelItemValues;
 
 class QJsonDocument;
 class QString;
diff --git a/formats/csvparser.cpp b/formats/csvparser.cpp
index 365de1d..85e5bac 100644
--- a/formats/csvparser.cpp
+++ b/formats/csvparser.cpp
@@ -86,7 +86,7 @@ QHash<QString, std::vector<std::string>> CsvParser::extractColumnValues(
     const rapidcsv::Document& doc) {
   QHash<QString, std::vector<std::string>> columnValueMap;
   for (const QString& columnName : headerNames) {
-    // NEXT add support for optional columns
+    // TODO add support for optional columns
     // if (optionalCsvHeaderNames.contains(columnName)) {
     //   const std::vector<std::string> columnNames = doc.GetColumnNames();
     //   int columnIdx                              = doc.GetColumnIdx(columnName.toStdString());
@@ -147,7 +147,7 @@ QVariant CsvParser::parseItemValue(const int role, const std::string& valueStrin
     result = doubleValue;
 
     // } else if (typeColumns.contains(columnName)) {
-    //   // NEXT validate string is allowed
+    //   // TODO validate string is allowed
     //   values[role] = QString::fromStdString(columnValueMap.value(columnName).at(row));
   } else {
     /// no type recognized for column
diff --git a/formats/csvparser.h b/formats/csvparser.h
index 7695156..b1375d9 100644
--- a/formats/csvparser.h
+++ b/formats/csvparser.h
@@ -3,7 +3,7 @@
 
 #include <QString>
 
-typedef QHash<int, QVariant> ModelItemValues;
+typedef QMap<int, QVariant> ModelItemValues;
 
 namespace rapidcsv {
 class Document;
diff --git a/formats/jsonparser.cpp b/formats/jsonparser.cpp
index a29f8e7..686f4bc 100644
--- a/formats/jsonparser.cpp
+++ b/formats/jsonparser.cpp
@@ -6,20 +6,35 @@
 #include "../model/metadata.h"
 
 QList<ModelItemValues> JsonParser::toItemValuesList(const QByteArray& jsonData,
-                                                    const QString& objectName) {
+                                                    const QString& rootValueName) {
   QList<ModelItemValues> result;
 
   if (jsonData.isEmpty()) {
     return result;
   }
 
-  QJsonArray itemArray = extractItemArray(jsonData, objectName);
+  // NEXT tidy up the following code and encapsulate into functions;
 
-  foreach (QJsonValue value, itemArray) {
-    QJsonObject itemJsonObject = value.toObject();
+  /// check if there is an array or there is only one object inside the root object;
+  // TODO ? rename objectName into jsonValueName?
+  if (rootValueName == ITEMS_KEY_STRING) {
+    QJsonArray itemArray = extractItemArray(jsonData, rootValueName);
+
+    foreach (QJsonValue value, itemArray) {
+      QJsonObject itemJsonObject = value.toObject();
+      ModelItemValues values     = jsonObjectToItemValues(itemJsonObject);
+      result.append(values);
+    }
+  }
+  if (rootValueName == ITEM_KEY_STRING) {
+    // QJsonArray itemArray = extractItemArray(jsonData, objectName);
+    QJsonDocument doc          = QJsonDocument::fromJson(jsonData);
+    QJsonObject rootObject     = doc.object();
+    QJsonObject itemJsonObject = rootObject.value(rootValueName).toObject();
     ModelItemValues values     = jsonObjectToItemValues(itemJsonObject);
     result.append(values);
   }
+
   return result;
 }
 
@@ -28,7 +43,7 @@ QByteArray JsonParser::itemValuesListToJson(const QList<ModelItemValues>& itemVa
   QJsonDocument jsonDoc;
   QJsonObject rootObject;
   QJsonArray itemArray;
-  for (const QHash<int, QVariant>& itemValues : itemValuesList) {
+  for (const ModelItemValues& itemValues : itemValuesList) {
     QJsonObject itemObject;
 
     QListIterator<UserRoles> i(USER_FACING_ROLES);
diff --git a/formats/jsonparser.h b/formats/jsonparser.h
index be0fc6a..a27d223 100644
--- a/formats/jsonparser.h
+++ b/formats/jsonparser.h
@@ -8,14 +8,14 @@ class QString;
 class QByteArray;
 class QJsonArray;
 
-typedef QHash<int, QVariant> ModelItemValues;
+typedef QMap<int, QVariant> ModelItemValues;
 
 using namespace std;
 
 class JsonParser {
  public:
   static QList<ModelItemValues> toItemValuesList(const QByteArray& jsonData,
-                                                 const QString& objectName = "");
+                                                 const QString& rootValueName = "");
   static QByteArray itemValuesListToJson(const QList<ModelItemValues>& itemValuesList,
                                          const QString& objectName = "");
 
diff --git a/genericcore.cpp b/genericcore.cpp
index 707037f..539e6ab 100644
--- a/genericcore.cpp
+++ b/genericcore.cpp
@@ -105,7 +105,7 @@ void GenericCore::saveItems() {
   qDebug() << "saving items...";
 
   const QJsonDocument doc   = m_mainModel->getAllItemsAsJsonDoc();
-  const bool successfulSave = FileHandler::saveToFile(doc, ITEM_FILE_NAME);
+  const bool successfulSave = FileHandler::saveToFile(doc, ITEMS_FILE_NAME);
   if (successfulSave) {
     m_modelUndoStack->setClean();
     emit displayStatusMessage(QString("Items saved."));
@@ -118,7 +118,7 @@ void GenericCore::importCSVFile(const QString& filePath) {
   qInfo() << "importing items from CSV...";
   qDebug() << "filePath:" << filePath;
   const QList<ModelItemValues> itemValuesList = FileHandler::getItemValuesFromCSVFile(filePath);
-  // NEXT inform UI on errors
+  // TODO inform UI on errors
   if (itemValuesList.isEmpty()) {
     qDebug() << "No items found. Doing nothing...";
     return;
@@ -149,7 +149,7 @@ void GenericCore::onSendItemTriggered(const QByteArray& jsonData) {
 void GenericCore::onItemsFetched(const QByteArray jsonData) {
   emit displayStatusMessage("New items fetched.");
   // TODO ? check compability of JSON structure beforehand?
-  // TODO check if item already exists?
+  // NEXT check if item already exists ? ;
   m_mainModel->appendItems(jsonData);
 }
 
@@ -157,8 +157,10 @@ void GenericCore::onItemsFetchFailure(const QString errorString) {
   emit displayStatusMessage(QString("Error: %1").arg(errorString));
 }
 
-void GenericCore::onPostRequestSuccessful(const QString message) {
-  // NEXT search local item an set server generated UUID
+void GenericCore::onPostRequestSuccessful(const QByteArray responseData) {
+  // NEXT search local item and set server generated UUID;
+  const QString message = m_mainModel->updateItemsFromJson(responseData);
+
   emit displayStatusMessage(message);
 }
 
@@ -193,7 +195,7 @@ void GenericCore::setupModels() {
  */
 void GenericCore::initModelData() {
   qInfo() << "Trying to read model data from file...";
-  const QByteArray jsonDoc = FileHandler::loadJSONDataFromFile(ITEM_FILE_NAME);
+  const QByteArray jsonDoc = FileHandler::loadJSONDataFromFile(ITEMS_FILE_NAME);
   // qDebug() << "jsonDoc:" << jsonDoc;
   // TODO decide on lack of file(s) (config, data) if example items should be generated
   //      (see welcome wizard)
@@ -228,7 +230,7 @@ void GenericCore::setupServerConfiguration() {
   /// request connections
   connect(this, &GenericCore::fetchItemsFromServer, m_serverCommunicator.get(),
           &ServerCommunicator::fetchItems);
-  connect(this, &GenericCore::sendItemToServer, this, &GenericCore::onSendItemTriggered);
+  connect(this, &GenericCore::postItemToServer, this, &GenericCore::onSendItemTriggered);
 
   /// response connections
   connect(m_serverCommunicator.get(), &ServerCommunicator::itemsFetched, this,
diff --git a/genericcore.h b/genericcore.h
index 9fc1e2a..66877f9 100644
--- a/genericcore.h
+++ b/genericcore.h
@@ -39,13 +39,13 @@ class GenericCore : public QObject {
   void onSendItemTriggered(const QByteArray& jsonData);
   void onItemsFetched(const QByteArray jsonData);
   void onItemsFetchFailure(const QString errorString);
-  void onPostRequestSuccessful(const QString message);
+  void onPostRequestSuccessful(const QByteArray responseData);
   void onPostRequestFailure(const QString errorString);
 
  signals:
   void displayStatusMessage(QString message);
   void fetchItemsFromServer();
-  void sendItemToServer(const QByteArray& jsonData);
+  void postItemToServer(const QByteArray& jsonData);
 
  private:
   QUndoStack* m_modelUndoStack;
diff --git a/model/commands/edititemcommand.cpp b/model/commands/edititemcommand.cpp
index 449272b..f9280f8 100644
--- a/model/commands/edititemcommand.cpp
+++ b/model/commands/edititemcommand.cpp
@@ -26,6 +26,11 @@ EditItemCommand::EditItemCommand(TableModel* model,
                         .arg(roleName)
                         .arg(index.data(DEFAULT_ROLE).toString())
                         .arg(value.toString());
+    } else if (role == IdRole) {
+      commandText = QString("Setting '%1' of item '%2' to '%3'")
+                        .arg(roleName)
+                        .arg(index.data(DEFAULT_ROLE).toString())
+                        .arg(value.toString());
     } else {
       qWarning() << "Role didn't match! Using a generic command text...";
       commandText = QString("Edit item '%1'").arg(index.data(DEFAULT_ROLE).toString());
diff --git a/model/commands/insertrowscommand.h b/model/commands/insertrowscommand.h
index ddc5617..64dff89 100644
--- a/model/commands/insertrowscommand.h
+++ b/model/commands/insertrowscommand.h
@@ -3,7 +3,7 @@
 
 #include <QUndoCommand>
 
-typedef QHash<int, QVariant> ModelItemValues;
+typedef QMap<int, QVariant> ModelItemValues;
 
 class TableModel;
 
diff --git a/model/commands/removerowscommand.h b/model/commands/removerowscommand.h
index 6703aab..21b314e 100644
--- a/model/commands/removerowscommand.h
+++ b/model/commands/removerowscommand.h
@@ -5,7 +5,7 @@
 
 class TableModel;
 
-typedef QHash<int, QVariant> ModelItemValues;
+typedef QMap<int, QVariant> ModelItemValues;
 
 class RemoveRowsCommand : public QUndoCommand {
  public:
diff --git a/model/metadata.h b/model/metadata.h
index ce42c60..eadb1d0 100644
--- a/model/metadata.h
+++ b/model/metadata.h
@@ -35,10 +35,11 @@ static QList<UserRoles> INT_ROLES    = {AmountRole};
 static QList<UserRoles> DOUBLE_ROLES = {FactorRole};
 
 /// JSON keys
-static const QString ITEM_KEY_STRING = "items";
+static const QString ITEMS_KEY_STRING = "items";
+static const QString ITEM_KEY_STRING  = "item";
 
 /// file naming
-static const QString ITEM_FILE_NAME = ITEM_KEY_STRING + ".json";
+static const QString ITEMS_FILE_NAME = ITEMS_KEY_STRING + ".json";
 
 /// functions
 static int GET_ROLE_FOR_COLUMN(const int column) {
diff --git a/model/modelitem.h b/model/modelitem.h
index 5d2e956..1019296 100644
--- a/model/modelitem.h
+++ b/model/modelitem.h
@@ -3,7 +3,7 @@
 
 #include <QVariant>
 
-typedef QHash<int, QVariant> ModelItemValues;
+typedef QMap<int, QVariant> ModelItemValues;
 
 class ModelItem {
  public:
@@ -18,7 +18,7 @@ class ModelItem {
   QJsonObject toJsonObject() const;
 
  private:
-  QHash<int, QVariant> m_values;
+  ModelItemValues m_values;
 };
 
 #endif  // MODELITEM_H
diff --git a/model/tablemodel.cpp b/model/tablemodel.cpp
index 6d97e03..0b3460f 100644
--- a/model/tablemodel.cpp
+++ b/model/tablemodel.cpp
@@ -29,7 +29,7 @@ QByteArray TableModel::generateExampleItems() {
 
     array.append(itemObject);
   }
-  rootObject.insert(ITEM_KEY_STRING, array);
+  rootObject.insert(ITEMS_KEY_STRING, array);
 
   doc.setObject(rootObject);
   return doc.toJson();
@@ -83,6 +83,7 @@ QVariant TableModel::data(const QModelIndex& index, int role) const {
     case InfoRole:
     case AmountRole:
     case FactorRole:
+    case IdRole:
       return m_items.at(row)->data(role);
     case ToStringRole:
       return m_items.at(row)->toString();
@@ -152,7 +153,7 @@ QJsonDocument TableModel::getAllItemsAsJsonDoc() const {
     QJsonObject itemObject = item->toJsonObject();
     array.append(itemObject);
   }
-  rootObject.insert(ITEM_KEY_STRING, array);
+  rootObject.insert(ITEMS_KEY_STRING, array);
 
   doc.setObject(rootObject);
   return doc;
@@ -175,11 +176,37 @@ QList<QStringList> TableModel::getItemsAsStringLists() const {
 QByteArray TableModel::jsonDataForServer(const QModelIndex& currentIndex) const {
   const QJsonObject itemObject = data(currentIndex, ToJsonRole).toJsonObject();
   QJsonObject rootObject;
-  rootObject.insert("item", itemObject);
+  rootObject.insert(ITEM_KEY_STRING, itemObject);
   const QJsonDocument jsonDoc(rootObject);
   return jsonDoc.toJson(QJsonDocument::Compact);
 }
 
+QString TableModel::updateItemsFromJson(const QByteArray& jsonData) {
+  /// convert JSON data into a list of item values
+  const QList<ModelItemValues> valueList = JsonParser::toItemValuesList(jsonData, ITEM_KEY_STRING);
+  /// for each item values:
+  // NEXT iterate over all value items in the list (or disable updating multiple items for now)
+  // for (ModelItemValues itemValues : valueList) {
+  // }
+  // NEXT encapsulate into updateItem(const ModelItemValues& itemValues)
+  QModelIndex foundIndex = searchItemIndex(valueList.first());
+
+  qDebug() << "Search done!";
+  if (foundIndex == QModelIndex()) {
+    const QString errorMessage = "No matching item found!";
+    qWarning() << errorMessage;
+    return errorMessage;
+  } else {
+    qInfo() << "Item found!";
+    /// update existing item
+    QMap<int, QVariant> roles = valueList.first();
+    setItemData(foundIndex, roles);
+    /// return status what happened in this function (i. e. "Created x items, updated y items.")
+    // return data(foundIndex, ToStringRole).toString();
+    return QString("Item found at row %1.").arg(foundIndex.row());
+  }
+}
+
 bool TableModel::removeRows(int firstRow, int nRows, const QModelIndex& parentIndex) {
   if (parentIndex != QModelIndex()) {
     qWarning() << "Removing of child rows is not supported yet!";
@@ -203,7 +230,7 @@ void TableModel::appendItems(const QByteArray& jsonDoc) { insertItems(-1, jsonDo
 void TableModel::insertItems(int startPosition,
                              const QByteArray& jsonDoc,
                              const QModelIndex& parentIndex) {
-  const QList<ModelItemValues> valueList = JsonParser::toItemValuesList(jsonDoc, ITEM_KEY_STRING);
+  const QList<ModelItemValues> valueList = JsonParser::toItemValuesList(jsonDoc, ITEMS_KEY_STRING);
 
   if (valueList.empty()) {
     /// don't try inserting if no values to insert
@@ -302,3 +329,60 @@ bool TableModel::isEmptyValueEqualToZero(const int role) const {
     return false;
   }
 }
+
+QModelIndex TableModel::searchItemIndex(const ModelItemValues givenItemValues) const {
+  // iterate over indexes to search item : see searchItem(...);
+  // for (const shared_ptr<ModelItem>& item : m_items) {
+  for (int row = 0; row < rowCount(); ++row) {
+    qDebug() << "Processing item at row" << row << "...";
+    QModelIndex itemIndex = index(row, 0);
+    if (isItemEqualToItemValues(itemIndex, givenItemValues)) {
+      qInfo() << "Found item at row" << row << "! Returning its index...";
+      return itemIndex;
+    }
+  }
+  qDebug() << "No matching item found. Returning empty pointer...";
+  return {};
+}
+
+bool TableModel::isItemEqualToItemValues(const QModelIndex& itemIndex,
+                                         const ModelItemValues givenItemValues) const {
+  /// do both have a UUID?
+  QVariant idOfItem = data(itemIndex, IdRole);
+  QVariant given    = givenItemValues.value(IdRole);
+  if (idOfItem.isValid() && given.isValid()) {
+    /// are the UUIDs the same?
+    if (idOfItem.toString() == given.toString()) {
+      qInfo() << "UUIDs are the same.";
+      return true;
+    } else {
+      qDebug() << "UUIDs are NOT the same.";
+      return false;
+    }
+  } else {
+    /// are all other values the same? (for now only USER_FACING_ROLES are checked)
+    QListIterator<UserRoles> i(USER_FACING_ROLES);
+    while (i.hasNext()) {
+      const UserRoles role       = i.next();
+      const QString roleName     = ROLE_NAMES.value(role);
+      const QVariant valueOfItem = data(itemIndex, role);
+      const QVariant givenValue  = givenItemValues.value(role);
+      if (STRING_ROLES.contains(role)) {
+        if (valueOfItem.toString() != givenValue.toString()) {
+          return false;
+        }
+      } else if (INT_ROLES.contains(role)) {
+        if (valueOfItem.toInt() != givenValue.toInt()) {
+          return false;
+        }
+      } else if (DOUBLE_ROLES.contains(role)) {
+        if (valueOfItem.toDouble() != givenValue.toDouble()) {
+          return false;
+        }
+      } else {
+        qCritical() << QString("Can't find data type for role %1!!!").arg(role);
+      }
+    }
+    return true;
+  }
+}
diff --git a/model/tablemodel.h b/model/tablemodel.h
index 4017d55..84c592f 100644
--- a/model/tablemodel.h
+++ b/model/tablemodel.h
@@ -8,7 +8,7 @@ class ModelItem;
 
 using namespace std;
 
-typedef QHash<int, QVariant> ModelItemValues;
+typedef QMap<int, QVariant> ModelItemValues;
 
 class TableModel : public QAbstractTableModel {
   Q_OBJECT
@@ -40,6 +40,8 @@ class TableModel : public QAbstractTableModel {
 
   QByteArray jsonDataForServer(const QModelIndex& currentIndex) const;
 
+  QString updateItemsFromJson(const QByteArray& jsonData);
+
  public slots:
   // bool insertRows(int position, int rows, const QModelIndex& parentIndex = QModelIndex())
   // override;
@@ -68,6 +70,9 @@ class TableModel : public QAbstractTableModel {
   QMap<int, QVariant> onlyChangedValues(const QModelIndex& index,
                                         const QMap<int, QVariant>& roleValueMap) const;
   bool isEmptyValueEqualToZero(const int role) const;
+  QModelIndex searchItemIndex(const ModelItemValues givenItemValues) const;
+  bool isItemEqualToItemValues(const QModelIndex& itemIndex,
+                               const ModelItemValues givenItemValues) const;
 };
 
 #endif  // TABLEMODEL_H
diff --git a/network/servercommunicator.cpp b/network/servercommunicator.cpp
index feb41ea..a48dae1 100644
--- a/network/servercommunicator.cpp
+++ b/network/servercommunicator.cpp
@@ -68,7 +68,7 @@ void ServerCommunicator::postItems(const QByteArray& jsonData) {
       QByteArray responseData = reply->readAll();
       const QString message   = QString("POST successful! Response: %1").arg(responseData);
       qInfo() << message;
-      emit postRequestSuccessful(message);
+      emit postRequestSuccessful(responseData);
     } else {
       const QString message = QString("Error: %1").arg(reply->errorString());
       qDebug() << message;
diff --git a/network/servercommunicator.h b/network/servercommunicator.h
index 257a4c8..6fdb7ba 100644
--- a/network/servercommunicator.h
+++ b/network/servercommunicator.h
@@ -26,7 +26,7 @@ class ServerCommunicator : public QObject {
 
   void itemsFetched(const QByteArray jsonDoc);
   void itemsFetchFailure(const QString errorString);
-  void postRequestSuccessful(const QString message);
+  void postRequestSuccessful(const QByteArray responseData);
   void postRequestFailure(const QString errorString);
 
  private: