Below is a guide on how to create a customised invoice.
From the main admin menu select 'Templates'.
And then 'Add' from the tool bar.
This will allow you to create a template for an Invoice, once you have entered the basic information select 'Save' from the tool bar.
Note: if you have already included tax in your products, select "Tax Already Included in xDRs". Conversely, if you want to add tax at the time the invoice is issued, select "Via Taxation Plugin".
You will then be presented with this page - select 'Layout Designer' to create a customised invoice.
Here you can create a tailored Invoice (opens only in Mozilla Firefox or Internet Explorer).
Be sure to save your changes before closing.
You can also select 'Help' for detailed information about each tab from the PortaBilling manual.