The physical nature of non‐additive forces in many‐atomic system and the methods of their calculations are discussed. The close recurrence formula which expresses the energy of m‐body interaction through the energies of 2,3,...,(m−1) bodies ones is obtained in the symmetry‐adapted perturbation theory and in the variational approach. The comparative analysis is given of the role of non‐additive forces for the stability of the atomic clusters with different electronic shells.