A final form of notification (email) is based on EJS. The procedure involves two steps: 

  1. The billing system generates the XML-file with the required data. 
  2. The XML-file is converted into the JSON-file that the EJS-template is applied to. As a result, the system generates the email in HTML. 

Navigate to SettingsMessage templates → select a message type → select a template → Edit to edit or test (Test) the existing template.

On the template test form you can see the source XML file — "Source document", the received HTML-file — "Generate a message", and the form that clients will see "Message in HTML format".