There are two types of notification: 1) When budget runs out (available time goes to zero), there is always an alarm, like for the typical system timer. 2) Optionally, you can enable a notification to nudge you slightly ealier, e.g. 10 minutes. This allows you to prepare to wrap up what you are doing so you can actually stop (e.g. in a "close the lid" sense) when time is up.