1. CaseFox supports placing a default message on invoices.  For adding a default message for all invoices for a selected client, click on "Clients" tab, select the client, then click on "Client Details/Edit" on the right side tabbed pane.  In "Text To Be Printed On Invoices Of This Client" enter the text to be printed on client's invoices.

Alternatively, you may also add a default text on all invoices for a selected case.  Select the case and then click on "Edit Case".  In description field, enter the default message within these tags:

[Invoice]your default message[/Invoice]

Alternatively, during invoice creation, you can add a message by clicking on "Message For Client" link.

2. For printing a tag line (or your tax id) under your address block on invoices, go to "Settings/Tools/Reports". Then click on "Edit Firm's Info".  Enter the text in "This Text Will Be Printed As It Is Under Your Address Block on PDF Invoices" box.