  In this paper we present a technique to reconstruct the scaling variables
defining $ep$ deep inelastic scattering by performing a kinematic fit. This
reconstruction technique makes use of the full potential of the data collected.
It is based on Bayes Theorem and involves the use of informative priors. The
kinematic fit method has been tested for the neutral current ep simulated
sample at a center of mass energy of 318 GeV with $Q^2$ > 400 GeV$^2$. In
addition to the scaling variables, this method is able to estimate the energy
of possible initial state radiation (E$_\gamma$ ) which otherwise goes
undetected. A better resolution than standard electron and double angle
techniques in the reconstruction of scaling variables is achieved using a
kinematic fit.
