The Group Five line of cases established the principle that the Tribunal's calculation of an administrative penalty under the Competition Act must be reasoned and capable of judicial review on rationality grounds. It did not establish a tariff. The Tribunal retains substantial discretion in how it weighs the considerations identified in the Act and in its own guidelines, and the Appeal Court has been measured in the degree to which it has been willing to intervene.

The more recent jurisprudence has begun to mark out the boundaries of that discretion. Penalty awards that depart materially from the Tribunal's own guidelines without a clearly articulated reason have been remitted for reconsideration. Aggravating factors that the Tribunal has identified must be reasoned in a way that connects them to the conduct rather than to the identity of the respondent. The treatment of mitigating factors — leniency, cooperation, compliance programmes — has become more structured.

For respondents, the practical consequence is that penalty mitigation is no longer a discretionary exercise to be invoked at the close of proceedings. It needs to be built into the structure of the response from the start: the compliance programme that pre-existed the conduct, the cooperation extended during the investigation, the evidence assembled to support each mitigating factor. These are matters of preparation, not of advocacy at hearing.

The longer-term question is whether the Tribunal's discretion in penalty calculation should remain as broad as it presently is, or whether the time has come for a more structured framework — perhaps codified, perhaps developed through guidelines with a stronger normative status. The arguments for greater structure are predictability and equality of treatment; the arguments against are flexibility and contextual responsiveness. Both have force, and the question may be one for legislative rather than judicial resolution.