  We present here the CP asymmetries in the decay rate and angular
distributions of $\tau\to K_S\pi\nu_\tau$ decays in the Standard Model (SM) and
beyond (BSM). The CP asymmetries in the SM are induced by the CP violation in
$K^0-\bar{K}^0$ mixing. To investigate the BSM CP-violating (CPV) effects, a
model-independent analysis is performed by using the low-energy effective field
theory (LEFT) framework at $\mu=2$~GeV. If one further assumes the BSM physics
to stem from above the electroweak scale, the LEFT shall then be matched onto
the SM effective field theory (SMEFT), the operators of which contributing to
$\tau\to K_S\pi\nu_\tau$ decays will also contribute to the neutron electric
dipole moment (EDM) and $D^0-\bar{D}^0$ mixing. The stringent bounds from the
latter suggest that no remarkable CPV effects can be observed in either the
decay rate or the angular distributions. The prospects for future measurements
of these observables are also mentioned.
