The Invoices feature of the Placements module can be configured from the Invoices Settings page in the main settings area of HA.  

General Settings

The General Settings tab contains all of the basic settings for invoices including the logo to be used on the invoice, the text of the invoice footer and the color scheme.  This tab is also where you can set the invoice admin(s) who will be notified on invoice-related emails.

Email Configuration Tab

Invoice-related emails can be configured from the Email Configuration tab within the Invoices Settings page.  For example, admins can turn Past Due Reminders on/off and admins can configure whether or not to turn Read Receipts on/off when emailing invoices externally.  

Read Receipts are turned off by default, however, Past Due Reminders are turned on by default.