There are three separate reminders that the system can send out for an outstanding invoice, though you can of course personalise your system to only send out the one or two if you prefer.
The reminders have been made highly customisable but can only be modified from the website. Once you're logged in, click on the 'Settings' tab then click on the 'Service Reminders and Email Templates' option.
Selecting any one of the above templates will allow you to edit them.
Down the first column you will see three buttons representing the invoice reminders that the system will send out to your customers. Clicking on any one of these will take you to a page allowing you to customise the wording of the reminder email, the number of days before it sends out another reminder and whether the reminder will also be CC'd to yourself.
Ensure that the invoice reminder is scheduled to be sent out automatically by selecting 'yes' from the drop down list of options and afterwards, click 'save'.
Now any future invoices you produce using the software will automatically send out reminders to the customer.