The Thomas--Reiche--Kuhn sum rule is used to form an effective potential that is added to the time-dependent configuration interaction singles (TDCIS) equations of motion in velocity gauge. The purpose of the effective potential is to include virtual coupling from singles to doubles, which is required for size-consistent velocity gauge TDCIS results. The proposed method is compared to length gauge TDCIS results for laser-assisted photoionization. Finally, a novel dynamical interference effect controlled by two-color fields is predicted for atomic targets.