Teachworks allows you to send an email to customers if they have an invoice that is about to become overdue. Invoice Due reminders are sent on the day that the invoice is due. You can set these notifications in your companies Account Settings. To enable overdue invoices, follow these instructions:
Go to the Account & Settings tab and click on Account Settings
Scroll down to the Invoice Settings section and set the Overdue Invoice Reminders to "Enabled".
Save the form.
You can customize the Overdue Invoice template by following the instructions here: Customizing Notification Templates.