The tool chk4upd checks if there is a newer version of GAMS available than the one you are running. It checks for the most recent version available as well as for the newest version you can run with your license in case your maintenance and support is expired.

By default it reads gamslice.txt located next to it. Alternatively, you can specify another license on the command line. In addition to the command line tool you will find an integration in the GAMS IDE at Help -> Check for GAMS Update.