Currently, we don't have automatic invoice notifications. However, the process of sending reminders is very easy. You can even add late fees.
From a functionality point of view, we felt there was a danger to your business relationships if email reminders were sent off without your knowledge. Instead, it's better to simply check your "late Invoices" list each week and send reminders with a personal note.
However, it's been requested a lot, so we are going to make this an option for users in the future.