When a case or matter is setup, you can choose payment terms (e.g., due on receipt, 30 days, 45 days).  System will keep track of over due invoices based on these payment terms.  Overdue notices can be downloaded in ready to be printed PDF/Word format for all overdue invoices by clicking on the OverDue Notices button on the Dashboard.

Individual overdue notices for invoices can be downloaded from the Unpaid Invoices section of the Dashboard, by clicking on the overdue days in each invoice line.  The overdue notice can be emailed to Client by clicking on EmailReminder link on the very right side in the invoice listing in the Unpaid Invoices section.