In essence, the rulings allow multinational entities in Belgium to reduce their corporate tax liability by "excess profits" that allegedly result from the advantage of being part of a multinational group. At this stage, the Commission has doubts if the tax provision complies with EU state aid rules, which prohibit the granting to certain companies of selective advantages that distort competition in the Single Market. The opening of an in-depth investigation gives interested third parties an opportunity to submit comments. It does not prejudge the outcome of the investigation.