This plugin from WPZA provides your website with invoicing user functionality to generate multiple invoices without any e-commerce functionality. Using an administrator’s account, you can generate and automatically email WordPress users (subscribers) that they have a new or updated invoice to view. Invoicing Plugin Features Bulk user invoicing; Global currency settings; Optional tax rates; Automatic emails upon invoice generation or change. Custom Theming To override the default invoice single and archive templates, simply copy the files from the plugin’s templates folder into your theme’s directory.