diff --git a/ui/BankingiOSApp/BankingiOSApp/Base.lproj/Localizable.strings b/ui/BankingiOSApp/BankingiOSApp/Base.lproj/Localizable.strings
index 9bd582a7..6260966f 100644
--- a/ui/BankingiOSApp/BankingiOSApp/Base.lproj/Localizable.strings
+++ b/ui/BankingiOSApp/BankingiOSApp/Base.lproj/Localizable.strings
@@ -49,6 +49,8 @@
 "TAN medium" = "TAN medium";
 "TAN hint from your bank:" = "Hint from your bank:";
 "Enter TAN:" = "TAN";
+"Decoding error" = "Decoding error";
+"Could not decode TAN challenge. Error: %@." = "Could not decode flicker code or QR code / PhotoTan. Most likely an internal error:\n%@.";
 "TAN medium change" = "TAN medium change";
 "TAN medium successfully changed to %@." = "TAN medium successfully changed to '%@'.";
 "Could not change TAN medium to %@. Error: %@." = "Could not change TAN medium to '%@'.\n\nError message from your bank:\n\n%@.";
diff --git a/ui/BankingiOSApp/BankingiOSApp/de.lproj/Localizable.strings b/ui/BankingiOSApp/BankingiOSApp/de.lproj/Localizable.strings
index 2651d069..1ea59098 100644
--- a/ui/BankingiOSApp/BankingiOSApp/de.lproj/Localizable.strings
+++ b/ui/BankingiOSApp/BankingiOSApp/de.lproj/Localizable.strings
@@ -49,6 +49,8 @@
 "TAN medium" = "TAN Medium";
 "TAN hint from your bank:" = "Hinweis Ihrer Bank:";
 "Enter TAN:" = "TAN";
+"Decoding error" = "Dekodierungsfehler";
+"Could not decode TAN challenge. Error: %@." = "Flicker code oder QR code / PhotoTan konnten nicht dekodiert werden. Sehr wahrscheinlich ein interner Fehler:\n%@.";
 "TAN medium change" = "TAN Medium Wechsel";
 "TAN medium successfully changed to %@." = "TAN Medium erfolgreich zu '%@' geändert.";
 "Could not change TAN medium to %@. Error: %@." = "TAN medium konnte nicht zu '%@' geändert werden.\n\nFehlermeldung Ihrer Bank:\n\n%@.";
diff --git a/ui/BankingiOSApp/BankingiOSApp/ui/views/EnterTanDialog.swift b/ui/BankingiOSApp/BankingiOSApp/ui/views/EnterTanDialog.swift
index 8d12bb52..a32296a7 100644
--- a/ui/BankingiOSApp/BankingiOSApp/ui/views/EnterTanDialog.swift
+++ b/ui/BankingiOSApp/BankingiOSApp/ui/views/EnterTanDialog.swift
@@ -77,6 +77,13 @@ struct EnterTanDialog: View {
         
         self.showFlickerCodeTanView = tanChallenge is FlickerCodeTanChallenge
         self.showImageTanView = tanChallenge is ImageTanChallenge
+        
+        if let decodingError = (tanChallenge as? FlickerCodeTanChallenge)?.flickerCode.decodingError {
+            showDecodingTanChallengeFailedErrorDelayed(decodingError)
+        }
+        if let decodingError = (tanChallenge as? ImageTanChallenge)?.image.decodingError {
+            showDecodingTanChallengeFailedErrorDelayed(decodingError)
+        }
     }
     
     
@@ -177,6 +184,21 @@ struct EnterTanDialog: View {
         }
     }
     
+    /**
+        This method gets called right on start up before dialog is shown -> Alert would get displayed before dialog and therefore covered by dialog -> delay displaying alert.
+     */
+    private func showDecodingTanChallengeFailedErrorDelayed(_ error: KotlinException?) {
+        DispatchQueue.main.asyncAfter(deadline: .now() + 1) {
+            self.showDecodingTanChallengeFailedError(error)
+        }
+    }
+    
+    private func showDecodingTanChallengeFailedError(_ error: KotlinException?) {
+        if let errorMessage = error?.message {
+            self.errorMessage = Message(title: "Decoding error", message: "Could not decode TAN challenge. Error: \(errorMessage).", primaryButton: .ok())
+        }
+    }
+    
     
     private func enteringTanDone() {
         let companion = EnterTanResult.Companion()