You can locate and edit this reminder by going to My Account > Notification Templates > click to edit Invoice Reminder.
Important: This invoice notification template is used ONLY for the invoices generated automatically based on client agreements with automated invoicing, where you check the option to send invoice reminders in the Invoicing tab of the agreement wizard. The template is not used for invoices outside this type of client agreements (like the product invoices, the manual invoices based on agreements, or the invoices created with the "Add Miscellaneous" button in BILLING TAB > Create Invoice).
To send a reminder for the latter types of invoices, you can either go to the client's Invoices file (CONTACTS TAB > Contact Name > Invoices tab) and use the "Re-send" option in the drop-down menu to the right of the respective invoice(s), or you can send a direct email to remind the client about the unpaid invoice(s).
**Note - the replacement tags will automatically fill in all the pertinent invoice information.**