The interest in non take-up of social benefit has increased during the last years in France as it is a relevant subject for social policy analysis. However such a phenomenon, by definition unobservable, rises many difficulties in terms of estimations. Identifying the non claimant to a benefit requires detailed and reliable databases with information on the individual incomes and household structure. In this paper we estimate the non take-up rate of a French means tested benefit the RSA " Revenu de solidarité active " using the European Union Statistics on Income and Living Conditions (EU-SILC). We aim to determine the characteristics of the non claimants and evaluate the probability for a household to participate in a welfare program. We use the longitudinal dimension to study the evolution of the take-up behaviour.