  Recently it has been speculated that the S-matrix elements on the world
volume of D$_3$-branes should satisfy the ward identity corresponding to the
S-duality transformations. For a single brane and in the low energy limit, this
indicates that in the abelian Dirac-Born-Indeld-Chern-Simons theory the
combination of contact terms and tree-level massless poles in an $n$-point
function should satisfy the S-duality. In this paper we examine in details the
S-matrix element of three gauge bosons and one two-form and the S-matrix
element of six gauge bosons in favor of the above proposal.
