Automatically Send Invoices to Customers
Do you want the ability to automatically send customers their invoice prior to it being due? You can with Unit Trac.
Step 1 - Go to Business > Settings > Notifications
Step 2 - Select 'Enable automatic invoicing' under the Upcoming Invoice Notifications section to automatically send an invoice by email to your customers before they are due;
Step 3 - Select the number of days ahead of the due date that you'd like to have your invoices emailed out.
Step 4 - Select your customers to receive the invoices by clicking 
and then selecting them from the listing of available customers with an email address.
For more info on customizing invoices see; add your logo help article, or add custom notes.