diff --git a/Corona-Warn-App/src/main/java/de/rki/coronawarnapp/ui/submission/SubmissionTanViewModel.kt b/Corona-Warn-App/src/main/java/de/rki/coronawarnapp/ui/submission/SubmissionTanViewModel.kt
index 50f093824f5905dcd86f77816ca5d30f2a64d58f..22b63d2d9bb3d827f9d70225c4d0677354dbb239 100644
--- a/Corona-Warn-App/src/main/java/de/rki/coronawarnapp/ui/submission/SubmissionTanViewModel.kt
+++ b/Corona-Warn-App/src/main/java/de/rki/coronawarnapp/ui/submission/SubmissionTanViewModel.kt
@@ -13,7 +13,11 @@ class SubmissionTanViewModel : ViewModel() {
 
         private const val TAN_LENGTH = 7
         private val EXCLUDED_TAN_CHARS = listOf('0', 'O', 'I', '1')
-        private val VALID_TAN_CHARS = ('A'..'Z').plus('0'..'9').minus(EXCLUDED_TAN_CHARS)
+        private val VALID_TAN_CHARS =
+            ('a'..'z')
+                .plus('A'..'Z')
+                .plus('0'..'9')
+                .minus(EXCLUDED_TAN_CHARS)
     }
 
     val tan = MutableLiveData<String?>(null)
diff --git a/Corona-Warn-App/src/main/java/de/rki/coronawarnapp/ui/submission/TanInput.kt b/Corona-Warn-App/src/main/java/de/rki/coronawarnapp/ui/submission/TanInput.kt
index 04c323b62d1f70c688e10bb2dbbb5f186437ebed..d1a251846533df73987b224954ebc59757d4869c 100644
--- a/Corona-Warn-App/src/main/java/de/rki/coronawarnapp/ui/submission/TanInput.kt
+++ b/Corona-Warn-App/src/main/java/de/rki/coronawarnapp/ui/submission/TanInput.kt
@@ -15,7 +15,6 @@ import kotlinx.android.synthetic.main.view_tan_input.view.tan_input_textview_4
 import kotlinx.android.synthetic.main.view_tan_input.view.tan_input_textview_5
 import kotlinx.android.synthetic.main.view_tan_input.view.tan_input_textview_6
 import kotlinx.android.synthetic.main.view_tan_input.view.tan_input_textview_7
-import java.util.Locale
 
 class TanInput(context: Context, attrs: AttributeSet) : FrameLayout(context, attrs) {
 
@@ -46,7 +45,7 @@ class TanInput(context: Context, attrs: AttributeSet) : FrameLayout(context, att
     }
 
     private fun updateTan(text: CharSequence?) {
-        this.tan = text?.toString()?.toUpperCase(Locale.getDefault())
+        this.tan = text?.toString()
         updateDigits()
         notifyListener()
     }
diff --git a/Corona-Warn-App/src/main/res/values/strings.xml b/Corona-Warn-App/src/main/res/values/strings.xml
index 4b9e03875307c0886b6bdca63062ae3512744333..a2024686375c087947db0701e7fea4430a4d2e0d 100644
--- a/Corona-Warn-App/src/main/res/values/strings.xml
+++ b/Corona-Warn-App/src/main/res/values/strings.xml
@@ -382,7 +382,7 @@
     <string name="submission_test_result_invalid_remove_test_button">Test entfernen</string>
     <!-- Submission Tan -->
     <string name="submission_tan_title">TAN Eingabe</string>
-    <string name="submission_tan_body">Geben Sie bitte die TAN Nummer ihres Befundes ein. Die TAN ist 7-stellig und Groß- und Kleinschreibung muss nicht beachtet werden.</string>
+    <string name="submission_tan_body">Geben Sie bitte die TAN Nummer ihres Befundes ein. Die TAN ist 7-stellig.</string>
     <string name="submission_tan_button_text">Weiter</string>
     <!-- Submission Intro -->
     <string name="submission_intro_title">Wurden Sie getestet?</string>