If you have received one of these don't worry you probably haven't got to fill it in. I phoned RSI and was told to throw it away and ignore any reminders as it is a mistake!! No wonder Mr Hollande thinks France needs extra fonctiionnaires....give me strength!
If you want to check, ring the number on the form and they will ask you for the number just above the bar code and tell you that you haven't got to fill it in.