French to English Other Business/Commerce (general) Post

This should be easy but am not quite sure what it is, or rather I can imagine a number of things it could be. Context is-the control of people who are on sick leave (to ensure that they are not cheating the system). An official may be sent round to where they are living, and if they are not at home they will be deemed to be in contravention of the rules. They have a chance to explain themselves in writing. The text is as follows:

Le contrôleur laisse à l'adresse de la personne contôlée une notice avec **envoi-reponse**, l'invitant à justifier le motif de son absence par écrit.."

There is probably a precise translation of **envoi-réponse**. I should be most grateful to anyone who knows it. Thanks as always in advance..
Yorick Jenkins