  We discuss the variation of the nuclear matrix element (NME) for the
neutrinoless double beta ($0\nu\beta\beta$) decay of $^{76}$Ge when the wave
functions are constrained to reproduce the experimental occupancies of the two
nuclei involved in the transition. In the Interacting Shell Model description
the value of the NME is enhanced about 15% compared to previous calculations,
whereas in the QRPA the NME's are reduced by 20%-30%. This diminishes the
discrepancies between both approaches. In addition, we discuss effect of the
short range correlations on the NME in the light of the recently proposed
parametrizations based on a consistent renormalization of the $0\nu\beta\beta$
transition operator.
