We are concerned with Lipschitzian error bounds and Lipschitzian stability properties for solutions of a complementarity system. For this purpose, we deal with a nonsmooth slack-variable reformulation of the complementarity system, and study conditions under which the reformulation serves as a local error bound for the solution set of the complementarity system. We also discuss conditions, guaranteeing metric regularity of the reformulation mapping, and investigate relations between the latter, and Lipschitzian stability properties for solutions of the complementarity system. Some special features of nonlinear complementarity problems are also discussed.