Article R3142-26 of the French Labour Code

The organisation responsible for the courses or sessions provided as part of the mutualist training leave will issue the employee with a certificate stating that the employee has actually attended the course.
This certificate is given to the employer when the employee returns to work.

Original in French 🇫🇷

Article R3142-26

L’organisme chargé des stages ou sessions dispensés dans le cadre du congé mutualiste de formation délivre au salarié une attestation constatant la fréquentation effective de celui-ci.
Cette attestation est remise à l’employeur au moment de la reprise du travail.