Specific features of the charge-transfer states and transitions of the O 2p → Co 3d type in octahedral complexes (CoO6)9− and (CoO6)10− are considered in the cluster approach. The reduced matrix elements of the electric dipole transition operator are calculated on the many-electron wave functions of the complexes corresponding to the initial (high-or low-spin) state and the final state at a charge-transfer transition. The energies of the many-electron charge-transfer transitions and their intensities are calculated within the Tanabe-Sugano theory taking into account the mixing of different configurations of the same symmetry. Simulation of the optical spectrum of cobaltites showed the presence of a wide band consisting of many lines due to the charge-transfer transitions. The results of the simulation are in agreement with experiment and demonstrate the limited validity of the generally accepted concepts of a simple structure of the spectrum of charge-transfer transitions.