We study the deeply virtual Compton scattering off a spin-one particle, as the case for the coherent scattering off a deuteron target. We extend our approach, formulated initially for a spinless case, and discuss the role of twist three contributions for restoring the gauge invariance of the amplitude. Using twist three contributions and relations, which emanate from the QCD equations of motion, we derive the gauge invariant amplitude for the deeply virtual Compton scattering (DVCS) off hadrons with spin 1. Using the derived gauge invariant amplitude, the single spin asymmetry is discussed. Throughout this paper, we deal with the U (1) gauge invariance of the amplitude rather than the SU (3)c gauge invariance. Concerning the QCD gauge, we fix it by choosing the axial gauge for gluons, A + = 0. 2 Actually, the method described in [11] and in this paper is suitable for a study of DVCS off an arbitrary spin hadron.