We report recent progress in the development of a new  computational method for X-ray absorption spectroscopy of d- and f- electron systems. The method combines eigenchannel R-matrix and multiple scattering formalisms. It enables us to take account of atomic multiplet-like
electron correlation effects in condensed systems,  on the basis of ab initio electron structure calculations. In this speech I will present the formalism and first results on the X-ray absorption at the L2,3 edge of Ca metal, where the spectral shape, and in particular the branching ratio, deviates strongly from that obtained in single-particle theory.