Software: QuickBooks accounting software
The Collections Centre helps you manage collecting payments from your customers. It lists all overdue and almost due invoices in a single place. You can send email reminders to one customer or many customers, and it tracks customer notes about your collection efforts.
— From QuickBooks help
From the “Sales & Customers” preferences (Company Preferences tab), check the “Enable Collections Centre” checkbox to turn on the Collections Centre feature.
Click the “Collections Centre” button from the Customer Centre page to get into the Collection Centre wizard.
From the Collections Centre, highlight the customer which you want to send the reminder email to and click the “Select and Send Email” link (on top).
On the following window, select the invoices which you want to send and amend the email body if required, then click the “Send” button to send the email.
Note: You may require to set up your email server from the “Send Forms” preferences (under My Preferences tab).