2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/60623We investigate the transfer of the Cohen-Macaulay property from a commutative ring to a subring of invariants under the action of a finite group. Our point of view is ring theoretic and not a priori tailored to a particular type of group action. As an illustration, we briefly discuss the special case of multiplicative actions, that is, actions on group algebras $k[\bbZ^n]$ via an action on $\bbZ^n$.15 pages, LaTeX with xypicCommutative Algebra13A50;16W22text