  To date, different alternative theories of gravity, although related,
involving Proca fields have been proposed. Unfortunately, the procedure to
obtain the relevant terms in some formulations has not been systematic enough
or exhaustive, thus resulting in some missing terms or ambiguity in the process
carried out. In this paper, we propose a systematic procedure to build the
beyond generalized theory for a Proca field in four dimensions containing only
the field itself and its first-order derivatives. We examine the validity of
our procedure at the fourth level of the generalized Proca theory. In our
approach, we employ all the possible Lorentz-invariant Lagrangian pieces made
of the Proca field and its first-order derivatives, including those that
violate parity, and find the relevant combination that propagates only three
degrees of freedom and has healthy dynamics for the longitudinal mode. The key
step in our procedure is to retain the flat space-time divergences of the
currents in the theory during the covariantization process. In the curved
space-time theory, some of the retained terms are no longer current divergences
so that they induce the new terms that identify the beyond generalized Proca
field theory. The procedure constitutes a systematic method to build general
theories for multiple vector fields with or without internal symmetries.
