Outsourcing information system development has become a common practice in companies. Many contributions were proposed for dealing with the management of such projects, and relationship between client and vendor. But little is known concerning the way to manage the change of service provider in an on-going project. Our study concerns the transition from an outgoing service provider to an incoming one during an outsourcing development project in a public institution. This transition mainly consists in transferring the project. The transfer involves not only materials (documents and code) but also knowledge. Based on literature on knowledge transfer, we exhibit good practices for the transition phase of an on-going outsourced project. We show how we applied these good practices on a -real- application case.