The invention relates to a method for automatically licensing service features during the upgrade of a first communication system (11) into a second communication system (12), said method having the following steps: (a) extracting the service features to be licensed from a database, (b) transmitting the service features to be licensed to a License Server (CLS), (c) generating a license file (LF) in the License server (CLS), (d) transmitting the license file (LF) to the second communication system (12), and (e) installing the license file (LF) in the second communication system (12). This invention also relates to a corresponding computer program and corresponding licensing system.