  We report high resolution polar Kerr effect measurements on CsV${}_3$Sb${}_5$
single crystals in search for signatures of spontaneous time reversal symmetry
breaking below the charge order transition at $T^* \approx 94$ K. Utilizing two
different versions of zero-area loop Sagnac interferometers operating at 1550
nm wavelength, each with the fundamental attribute that without a time reversal
symmetry breaking sample at its path, the interferometer is perfectly
reciprocal, we find no observable Kerr effect to within the noise floor limit
of the apparatus at 30 nanoradians. Simultaneous coherent reflection ratio
measurements confirm the sharpness of the charge order transition in the same
optical volume as the Kerr measurements. At finite magnetic field we observe a
sharp onset of a diamagnetic shift in the Kerr signal at $T^*$, which persists
down to the lowest temperature without change in trend. Since 1550 nm is an
energy that was shown to capture all features of the optical properties of the
material that interact with the charge order transition, we are led to conclude
that it is highly unlikely that time reversal symmetry is broken in the charge
ordered state in CsV${}_3$Sb${}_5$.
