Teachworks allows you to send an email to customers if they have an overdue invoice. Overdue invoices reminders are sent on the day after the invoice is due. Overdue invoice notifications are set 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.