One of the most interesting channels to search for SUSY is the direct pair-production of
the $\tau$-lepton superpartner, $\widetilde{\tau}$. The $\widetilde{\tau}$ is with
high probability the lightest of the scalar leptons, so one of the first SUSY particles that can
be observerd, and the signature of $\widetilde{\tau}$ pair production signal events is one of the
most difficult ones, yielding to the ``worst'' and so most global scenario for the searches.
Analysis performed at LEP set the current model-independent $\widetilde{\tau}$ limits, suffering
from the low energy of this facility. Only under strong model assumptions, these limits are extended to
higher masses by LHC studies.
In this contribution we show the capability of the ILC, a future electron-positron collider with
energy up to 1 TeV, for determining $\widetilde{\tau}$ exclusion/discovery limits in a
model-independent way, including an overview of the current state-of-the-art.
The determination of the ``worst'' scenario for $\widetilde{\tau}$ exclusion/discovery, taking
into account the effect of the $\widetilde{\tau}$ mixing on $\widetilde{\tau}$ production
cross-section and efficiency, is also presented.
For selected benchmarks, the prospect for measuring masses
and polarised cross-sections will be shown. The studies were done studying events passed through the
full detector simulation and reconstruction procedures of the International Large Detector (ILD) concept
at the ILC. The simulation included all SM backgrounds, as well as the machine induced ones.