  The main theoretical tool to provide precise predictions for scattering cross
sections of strongly interacting particles is perturbative QCD. Starting at
next-to-leading order (NLO) the calculation suffers from unphysical
IR-divergences that cancel in the final result. At NLO there exist general
subtraction algorithms to treat these divergences during a calculation. Since
the LHC demands for more precise theoretical predictions, general subtraction
methods at next-to-next-to-leading order (NNLO) are needed. This proceeding
outlines the four-dimensional formulation of the sector improved residue
subtraction. The subtraction scheme STRIPPER and in particular its extension to
arbitrary multiplicities is explained. Therefore, it furnishes a general
framework for the calculation of NNLO cross sections in perturbative QCD.
