diff --git a/messages/uniworx/categories/courses/courses/de-de-formal.msg b/messages/uniworx/categories/courses/courses/de-de-formal.msg
index 85acabc35..764150b5a 100644
--- a/messages/uniworx/categories/courses/courses/de-de-formal.msg
+++ b/messages/uniworx/categories/courses/courses/de-de-formal.msg
@@ -114,9 +114,9 @@ CourseParticipantsRegisterTutorialOption: Kursteilnehmer:innen zu Übungsgruppe
 CourseParticipantsRegisterTutorialField: Übungsgruppe
 CourseParticipantsRegisterTutorialFieldTip: Ist aktuell keine Übungsgruppe mit diesem Namen vorhanden, wird eine neue erstellt. Ist bereits eine Übungsgruppe mit diesem Namen vorhanden, werden die Kursteilnehmenden dieser hinzugefügt.
 CourseParticipantsRegisterNoneGiven: Es wurden keine anzumeldenden Personen angegeben!
+CourseParticipantsRegisterNotFoundInAvs n@Int: #{n} #{pluralDE n "Person" "Personen"} konnten nicht im AVS gefunden werden
 
 CourseParticipantsInvited n@Int: #{n} #{pluralDE n "Einladung" "Einladungen"} per E-Mail verschickt
-CourseParticipantsAddedByAvs n@Int: #{n} AVS-Nutzer erfolgreich angemeldet (TODO)
 CourseParticipantsAlreadyRegistered n@Int: #{n} #{pluralDE n "Teinehmer:in" "Teilnehmer:innen"} #{pluralDE n "ist" "sind"} bereits angemeldet
 CourseParticipantsAlreadyTutorialMember n@Int: #{n} #{pluralDE n "Teinehmer:in" "Teilnehmer:innen"} #{pluralDE n "ist" "sind"} bereits in dieser Übungsgruppe angemeldet
 CourseParticipantsRegistered n@Int: #{n} #{pluralDE n "Teinehmer:in" "Teilnehmer:innen"} erfolgreich angemeldet
diff --git a/messages/uniworx/categories/courses/courses/en-eu.msg b/messages/uniworx/categories/courses/courses/en-eu.msg
index 2fbddbd73..81d678c44 100644
--- a/messages/uniworx/categories/courses/courses/en-eu.msg
+++ b/messages/uniworx/categories/courses/courses/en-eu.msg
@@ -114,9 +114,9 @@ CourseParticipantsRegisterTutorialOption: Register course participants for tutor
 CourseParticipantsRegisterTutorialField: Tutorial
 CourseParticipantsRegisterTutorialFieldTip: If there is no tutorial with this name, a new one will be created. If there is a tutorial with this name, the course participants will be registered for it.
 CourseParticipantsRegisterNoneGiven: No persons given to register!
+CourseParticipantsRegisterNotFoundInAvs n: #{n} #{pluralEN n "person" "persons"} could not be found in AVS
 
 CourseParticipantsInvited n: #{n} #{pluralEN n "invitation" "invitations"} sent via email
-CourseParticipantsAddedByAvs n: #{n} AVS users successfully registered (TODO)
 CourseParticipantsAlreadyRegistered n: #{n} #{pluralEN n "participant is" "participants are"} already enrolled
 CourseParticipantsAlreadyTutorialMember n: #{n} #{pluralEN n "participant is" "participants are"} already registered for this tutorial
 CourseParticipantsRegistered n: Successfully registered #{n} #{pluralEN n "participant" "participants"}
diff --git a/src/Handler/Course/ParticipantInvite.hs b/src/Handler/Course/ParticipantInvite.hs
index b2c0ece45..8190b0905 100644
--- a/src/Handler/Course/ParticipantInvite.hs
+++ b/src/Handler/Course/ParticipantInvite.hs
@@ -27,7 +27,8 @@ import Generics.Deriving.Monoid (memptydefault, mappenddefault)
 
 
 data AddParticipantsResult = AddParticipantsResult
-  { aurAlreadyRegistered
+  { aurNotFound              :: Set Text
+  , aurAlreadyRegistered
   , aurAlreadyTutorialMember
   , aurRegisterSuccess
   , aurTutorialSuccess       :: Set UserId
@@ -83,13 +84,18 @@ registerUsers cid usersToRegister = do
       -> tell . pure =<< messageI Error MsgCourseParticipantsRegisterNoneGiven
     | otherwise
       -- register retrieved users
-      -> tell <=< lift . addParticipantsResultMessages <=< lift . execWriterT $ mapM_ (registerUser cid) (catMaybes $ Map.elems avsUsers)
+      -> tell <=< lift . addParticipantsResultMessages <=< lift . execWriterT . mapM_ (registerUser cid) $ Map.toList avsUsers
 
 
 addParticipantsResultMessages :: (MonadHandler m, HandlerSite m ~ UniWorX)
                               => AddParticipantsResult
                               -> ReaderT (YesodPersistBackend UniWorX) m [Message]
 addParticipantsResultMessages AddParticipantsResult{..} = execWriterT $ do
+  unless (null aurNotFound) $ do
+    let modalTrigger = [whamlet|_{MsgCourseParticipantsRegisterNotFoundInAvs (length aurNotFound)}|]
+        modalContent = $(widgetFile "messages/courseInvitationNotFoundInAvs")
+    tell . pure <=< messageWidget Error $ msgModal modalTrigger (Right modalContent)
+
   aurAlreadyRegistered'     <- fmap sort (lift . mapM getJust $ Set.toList aurAlreadyRegistered)
   aurAlreadyTutorialMember' <- fmap sort (lift . mapM getJust $ Set.toList aurAlreadyTutorialMember)
 
@@ -109,9 +115,10 @@ addParticipantsResultMessages AddParticipantsResult{..} = execWriterT $ do
 
 
 registerUser :: CourseId
-             -> UserId
+             -> (Text, Maybe UserId)
              -> WriterT AddParticipantsResult (YesodJobDB UniWorX) ()
-registerUser cid uid = exceptT tell tell $ do
+registerUser _cid ( avsIdent, Nothing ) = tell $ mempty { aurNotFound = Set.singleton avsIdent }
+registerUser  cid (_avsIdent, Just uid) = exceptT tell tell $ do
   whenM (lift . lift $ exists [CourseParticipantCourse ==. cid, CourseParticipantUser ==. uid, CourseParticipantState ==. CourseParticipantActive]) $
     throwError $ mempty { aurAlreadyRegistered = Set.singleton uid }
 
diff --git a/templates/messages/courseInvitationNotFoundInAvs.hamlet b/templates/messages/courseInvitationNotFoundInAvs.hamlet
new file mode 100644
index 000000000..558b8469a
--- /dev/null
+++ b/templates/messages/courseInvitationNotFoundInAvs.hamlet
@@ -0,0 +1,12 @@
+$newline never
+
+$# SPDX-FileCopyrightText: 2022 Sarah Vaupel <sarah.vaupel@ifi.lmu.de>
+$#
+$# SPDX-License-Identifier: AGPL-3.0-or-later
+
+<h2>
+  _{MsgCourseParticipantsRegisterNotFoundInAvs (length aurNotFound)}
+<ul>
+  $forall userNotFound <- aurNotFound
+    <li>
+      #{userNotFound}