It is shown that the neglect of the Coulomb repulsion between colliding ions introduces negligible errors in calculations on excitation and ionization cross sections except in the very early part of the (cross section)-(impact energy) curves. For example, in the case of He⁺(1s) + He²⁺ → He⁺(2s) + He²⁺ the fractional correction which should be made to the first Born approximation to the cross section is as low as 5% at the smaller of the two energies at which the cross section is one quarter the maximum, and is as low as 0.3% at the energy at which the cross section passes through the maximum. The corresponding fractional corrections for the 1s-2p transitions are even less.