If the Skype for Business you have is a part of Microsoft Office or is the Office 365 Skype for Business, Skype for Business won’t even show up as a program you can uninstall in the Control Panel as it is integrated into all of your other Office applications. If you do have a standalone version of Skype for Business, however, you can.
Try using a free uninstall tool like. If you already threw the app in the trash, counterintutively, you'd need to reinstall it to get AppCleaner to work.There are a few standard places where packaged apps install their files, but it's not easy to look by hand. There's your library, the system library, and so on. I feel it's better to automate this process than attempt to do it by hand.Another option is a cleanup tool like CleanMyMac, it's a paid tool, but is built for removing application remnants.