This article presents a new delay-dependent condition to design a Kalman/Luenberger-type filter for neutral systems. Where the resulting filter is such that a prescribed [image omitted] level is guaranteed. The proposed approach is based on linear matrix inequalities and on Lyapunov-Krasovskii theory. Also, the Gu's discretisation method and a slack matrix technique, that decouples the system matrices from the Lyapunov ones, are applied in order to obtain less conservative results than the similar ones. Two numerical examples are performed to illustrate the advantage of the method proposed.