  We present a modified spin algorithm, including spin correlations, which has
been implemented in {\tt ee$\in$MC} for the simulation of $e^{+}e^{-} \to
\tau^{+}\tau^{-} (\gamma)$ events with an arbitrary initial spin configuration.
This algorithm is suitable for the proposed BELLE-II polarization upgrade to
SuperKEKB, both for the ideal case and for the case where there are
misalignments, radiative effects and allows for changing polarization
conditions. The spin $1/2$ states of the polarized beams are constructed in
terms of a super-positioning of the helicity states corresponding to the
polarimetric-vector describing the overall beam polarization and implemented
both through a modification of the initial state in the modified
Altrelli-Parsis Density Function as well as a change of basis of the helicity
states.
