diff --git a/akonadi/calendar/calendarbase.cpp b/akonadi/calendar/calendarbase.cpp
--- a/akonadi/calendar/calendarbase.cpp
+++ b/akonadi/calendar/calendarbase.cpp
@@ -229,7 +229,7 @@
                  << "Please fix it. Ignoring this incidence.";
         return;
     }
-    const QString calendar = QString::number(item.storageCollectionId());
+    const QString calendar = QString::number(item.parentCollection().id());
     const QString uniqueInstanceIdentifier =  calendar + incidence->instanceIdentifier();
 
     if (mItemIdByUniqueInstanceIdentifier.contains(uniqueInstanceIdentifier) && mItemIdByUniqueInstanceIdentifier[uniqueInstanceIdentifier] != item.id()) {
@@ -273,6 +273,11 @@
     mItemIdByUniqueInstanceIdentifier.insert(uniqueInstanceIdentifier, item.id());
     mItemsByCollection.insert(item.storageCollectionId(), item);
 
+    // we need item in storageCollection, to find exceptions
+    if (item.parentCollection().id() != item.storageCollectionId()) {
+        mItemsByCollection.insert(item.parentCollection().id(), item);
+    }
+
     incidence->setCustomProperty("VOLATILE", "AKONADI-ID", QString::number(item.id()));
     // Must be the last one due to re-entrancy
     const bool result = q->MultiCalendar::addIncidenceToCalendar(calendar, incidence);
@@ -322,7 +327,7 @@
     }
     Q_ASSERT(item.storageCollectionId() > 0);
 
-    const QString calendar = QString::number(item.storageCollectionId());
+    const QString calendar = QString::number(item.parentCollection().id());
     const QString uniqueInstanceIdentifier = calendar + tmp->instanceIdentifier();
 
     // We want the one stored in the calendar
@@ -331,11 +336,10 @@
     // Null incidence means it was deleted via CalendarBase::deleteIncidence(), but then
     // the ETMCalendar received the monitor notification and tried to delete it again.
     if (incidence) {
-        mItemById.remove(item.id());
         // kDebug() << "Deleting incidence from calendar .id=" << item.id() << "uid=" << incidence->uid();
         mItemIdByUniqueInstanceIdentifier.remove(uniqueInstanceIdentifier);
 
-        mItemsByCollection.remove(item.storageCollectionId(), item);
+        mItemsByCollection.remove(item.parentCollection().id(), item);
 
         // Must be the last one due to re-entrancy
         // This will trigger the removal of all exceptions via deleteIncidence
@@ -344,6 +348,13 @@
             kError() << "Error removing incidence " << itemToString(item);
             Q_ASSERT(false);
         }
+
+        // only remove ItemById entry if all incidences are deleted
+        // we need item in storageCollection, to find exceptions
+        if (mItemIdByUniqueInstanceIdentifier.key(item.id(), QString()).isEmpty()) {
+            mItemById.remove(item.id());
+            mItemsByCollection.remove(item.storageCollectionId(), item);
+        }
     } else {
         kWarning() << "CalendarBase::internalRemove2: incidence is null, item.id=" << itemToString(item);
     }
@@ -391,7 +402,7 @@
     if (resultCode == IncidenceChanger::ResultCodeSuccess && !mListensForNewItems) {
         Q_ASSERT(item.isValid());
         Q_ASSERT(item.hasPayload<KCalCore::Incidence::Ptr>());
-        //FIXME fetch, otherwise we don't have the storageCOllectionId
+        //FIXME fetch, otherwise we don't have the storageCollectionId
         internalInsert(item);
     }
 
@@ -412,7 +423,7 @@
         KCalCore::Incidence::Ptr incidence = CalendarUtils::incidence(item);
         Q_ASSERT(incidence);
         Q_ASSERT(item.storageCollectionId() > 0);
-        const QString calendar = QString::number(item.storageCollectionId());
+        const QString calendar = QString::number(item.parentCollection().id());
 
         // We want the one stored in the calendar
         KCalCore::Incidence::Ptr localIncidence = q->incidence(calendar, incidence->uid(), incidence->recurrenceId());
@@ -439,7 +450,7 @@
     Incidence::Ptr oldIncidence = CalendarUtils::incidence(oldItem);
     Q_ASSERT(oldIncidence);
 
-    const QString calendar = QString::number(newItem.storageCollectionId());
+    const QString calendar = QString::number(newItem.parentCollection().id());
     const QString uniqueInstanceIdentifier =  calendar + newIncidence->instanceIdentifier();
     if (mItemIdByUniqueInstanceIdentifier.contains(uniqueInstanceIdentifier)) {
         Incidence::Ptr oldIncidence = CalendarUtils::incidence(oldItem);
@@ -481,7 +492,7 @@
         return;
     }
 
-    const QString oldCalendar = QString::number(oldItem.storageCollectionId());
+    const QString oldCalendar = QString::number(oldItem.parentCollection().id());
     const QString oldUniqueInstanceIdentifier =  oldCalendar + oldIncidence->instanceIdentifier();
     mItemIdByUniqueInstanceIdentifier.remove(oldUniqueInstanceIdentifier);
     const QString oldUid = oldIncidence->uid();
diff --git a/akonadi/calendar/etmcalendar.cpp b/akonadi/calendar/etmcalendar.cpp
--- a/akonadi/calendar/etmcalendar.cpp
+++ b/akonadi/calendar/etmcalendar.cpp
@@ -432,14 +432,14 @@
     Q_ASSERT(!newIncidence->uid().isEmpty());
     newIncidence->setCustomProperty("VOLATILE", "AKONADI-ID", QString::number(item.id()));
     Q_ASSERT(item.storageCollectionId() >= 0);
-    IncidenceBase::Ptr existingIncidence = q->incidence(QString::number(item.storageCollectionId()), newIncidence->uid(), newIncidence->recurrenceId());
+    IncidenceBase::Ptr existingIncidence = q->incidence(QString::number(item.parentCollection().id()), newIncidence->uid(), newIncidence->recurrenceId());
 
     if (!existingIncidence && !mItemById.contains(item.id())) {
         // We don't know about this one because it was discarded, for example because of not having DTSTART
         return;
     }
 
-    mItemsByCollection.insert(item.storageCollectionId(), item);
+    mItemsByCollection.insert(item.parentCollection().id(), item);
     Akonadi::Item oldItem = mItemById.value(item.id());
 
     if (existingIncidence) {