The experimental precision achievable in modern experiments on ep-scattering
allows for measuring the cross section and spin asymmetries in Bethe-Heitler
(BH) and semi-inclusive deep inelastic scattering (SIDIS) processes with
unprecedented accuracies. The QED radiative correction is one serious source
of systematical uncertainties and therefore must be known with any
predetermined accuracy. Several available calculations provide only leading
logarithm accuracy (for BH), performed only for unpolarized target (for SIDIS),
and/or have certain other limitations. In this report we present the results
of exact calculation of RC for BH process for unpolarized target as well as
for both longitudinally and transversely polarized targets. Details of the
calculations of the three key components such as i) the calculation of the
cross section of two-photon-emission process and analytic integration over
additional kinematical variables, ii) extraction of infrared divergence using
the dimensional regularization, and iii) calculation of loop effects with
extraction and complete cancellation of the infrared divergence, are discussed.
Also we present an approach for exact calculation of RC in semi-inclusive
process. The general task of exactly calculated RC in semi-inclusive processes
for arbitrary target polarization requires the calculation of the covariant
SIDIS hadronic tensor, important intermediate quantity. Recent results for its
calculation are presented and discussed.