  The Master Ward Identity (MWI) gives a universal formulation of the
symmetries of a classical field theory. It is a renormalization condition for
the time ordered products of the corresponding quantum field theory. We show
that the MWI for a complex scalar field with quartic interaction can be
satisfied, with the current, the interaction and all their submonomials as
allowed arguments. The proof is performed in the framework of deformation
quantization combined with causal perturbation theory, which is summarized and
introduced. Some examples of Ward Identities following from the proven MWI are
given.
