Turn off toast notifications on the lock screen This policy setting turns off toast notifications on the lock screen. If you enable this policy setting, applications will not be able to raise toast notifications on the lock screen. If you disable or do not configure this policy setting, toast notifications on the lock screen are enabled and can be turned off by the administrator or user. No reboots or service restarts are required for this policy setting to take effect.

(1) GPO: User Configuration\Administrative Templates\Start Menu and Taskbar\Notifications!Turn off toast notifications on the lock screen (2) REG: HKEY_CURRENT_USER\SOFTWARE\Policies\Microsoft\Windows\CurrentVersion\PushNotifications!NoToastApplicationNotificationOnLockScreen