If charge is expressed in terms of e, i.e. electronic charge 1.6×10-19 Coulomb,
then the charge of any particle is referred as so many times of smallest possible charge in atomic level .
Hence no fraction of electronic charge exist in nature at atomic level. In sub atomic level, though neutron has net zero charge,
it is made up of three quarks having charge of -(1/3)e, -(1/3)e and +(2/3)e .
Hence theoretically, particles exist with magnitude of charge less than the magnitude of electronic charge at sub-atomic level.
In general physical measurement of absolute charge is rare. Even gold leaf electroscope gives reference value only.
hence measurement of charge less than electronic charge is not possible.Hence we do not express charge as fraction of e.
Just for these reason we can not say charge is quantised.
Photon energy is quantised by physics( Plank's Radiation theory), But physics do not quantise electrical charges