To tell if you have SliQ Invoicing Lite or SliQ Invoicing Plus, check the desktop icon you use to launch the program. The text under the icon will show the name of the program. Alternatively, if you are running SliQ, check the title bar at the top of the program: does it say SliQ Invoicing Plus or Lite?
To check the specific version of the package you are using, e.g. is it 2.1, 3.3 and so on, there are two ways:-
1. The first way is to check the desktop icon. If the package name under the icon ends in 3 then you are using SliQ Invoicing Plus version 3.
2. If you are running SliQ then go to the Setup tab and press the About button in the toolbar. SliQ will then show the About dialog with the exact version number at the top of the dialog.