ABSTRACT Cross-sections and rate coefficients for the partial inelastic processes in calcium–hydrogen collisions are calculated by means of the quantum reprojection method for nuclear dynamics based on the accurate ab initio electronic structure data. That is, the atomic data for the 110 inelastic processes of excitation, de-excitation, ion-pair formation, and mutual neutralization in Ca  + H and Ca+  + H− collisions are computed for all transitions between the 11 low-lying CaH(2Σ+) molecular states including ionic one. The quantum chemical data are used in a hybrid diabatic representation, which is derived from the adiabatic representation. It is found that the largest rate coefficients correspond to the mutual neutralization processes. At the temperature 6000 K, the maximal rate is equal to $4.37 \times 10^{-8}\, \mathrm{cm}^{3}\,\mathrm{s}^{-1}$. It is shown that the large-valued rates are determined by long-range ionic–covalent interactions with final binding energies from the optimal window, while moderate- and low-valued rates by both long- and short-range non-adiabatic regions with final energies outside of the optimal window.