For overdue payments, Invoice Simple gives you the ability to email reminders to your clients. You can send as many reminders as you deem necessary. Here’s how to send reminders.
If an invoice is overdue, you will see a Send Reminder button on the edit screen.
Hitting the button will take you to a compose message window where you can create a custom reminder message for your client
Once you have composed the message, hit the send button in the lower left.