  The influence of the hard photon emission on the charge asymmetry in the
(anti)lepton-proton elastic scattering was evaluated for the first time beyond
the ultrarelativistic limit, while retaining the lepton mass at all steps of
the calculation. This contribution - responsible for the charge asymmetry - is
induced by interference between real photon emission from the lepton and
proton. During the calculation any excited states of the intermediated proton
are not considered, allowing us to use the standard fermionic propagator for
this particle. The infrared divergence extracted using Lorenz-invariant
approach of Bardin-Shumeiko is canceled by the corresponding soft part of the
two-photon exchange contribution. Numerical analysis was performed within
kinematic conditions of Jefferson Lab measurements and MUSE experiment in PSI.
