We present high resolution photoemission studies of Sn on vicinal Si(100)2x1 surface in submonolayer regime. Deposition of Sn on clean Si(100) surface produces an abrupt epitaxial interface having a large variety of surface reconstructions. At room temperature at low coverages Sn dimer rows are formed. After annealing above 500 o C following superstructures are known to exist with increasing Sn coverage: c(4x4), 2x6, c(4x8), and 1x5. The Sn4d core level spectra are now resolved in details displaying new components related to the different adsorption sites on the Si(100) surface. The spectra of the annealed phase reconstructions show components originating from dimer bonding, from bonding to the second layer, from Sn atoms in mixed Sn-Si dimers where Sn atoms have replaced one of the Si dimer pair atoms, and from adsorption onto defect sites. The photoemission results are in good agreement with the surface geometric structures.