In order to change Invoice name to " TAX Invoice ", please find the below steps for the same.
Path: eZee configuration >> Go to the advance setting >> Printing >> Print Folio Option >> Click on abc button.
Step 1: (To get this option, language pack should be activated)(Visit Live Support, if it is not activated in your property)
Step 2: Change Invoice caption on custom 1 language From "INVOICE" to "TAX INVOICE".
Step 3: Now go to the user setting and assign custom 1 language to the user.
Step 4: Now restart Front desk and print the Folio and it will print Tax Invoice as per bellow screenshot.