  We explore the idea of accidental dark matter (aDM) stability in the scale
invariant local $U(1)_{B-L}$ model, which is a theory for neutrino and at the
same time radiatively breaks scale invariance via quantum mechanical dynamics
in the $U(1)_{B-L}$ sector. A real singlet scalar can be accidental DM with an
accidental $Z_2$, by virtue of both extended symmetries. A $U(1)_{B-L}$ charged
complex scalar can also be a viable accidental DM due to an accidental (or
remanent) $Z_3$. They can reproduce correct relic density via the annihilations
through the conventional Higgs portal or dark Higgs portal. The dark Higgs
portal scenario is in tension with the LHC bound on $Z_{B-L}$, and only heavy
DM of a few TeVs can have correct relic density. In particular, DM may trigger
spontaneous breaking of scale Invariance (SISB). The situation is relaxed
significantly in the $Z_3$ case due to the effective semi-annihilation mode and
then light DM can be accommodated easily. In addition, the $Z_3$ model can
accommodate the GeV scale $\gamma-$ray excess from the galactic center (GC) via
semi-annihilation into pseudo Goldstone boson (PGSB). The best fit is achieved
at a DM about 52 GeV, with annihilation cross section consistent with the
thermal relic density. The invisible Higgs branching ratio is negligible
because the Higgs portal quartic coupling is very small $\lambda_{h\phi}
\lesssim 10^{-3}$.
