Class proceedings legislation in Canada has generally been described as a change in our procedural law, not a change in our substantive law. Where it is preferable to do so, class proceedings legislation allows a court to appoint a representative plaintiff to represent an entire class in a proceeding. However, the substantive elements of the contractual or other cause of action still needs to be fully proven, either as a common issue or based upon individual inquiries.

These rules made certain types of claims a poor match for the class proceedings process. For example, certain types of “mass contract” claims, such as claims involving the calculation of fees and charges in client accounts, necessarily involved substantial individualized calculation. For example, the method of calculation under challenge in a particular case might be unfavourable to some clients but beneficial to others. As a further example in some cases liability will depend upon whether a client would have approved the arrangement if asked. In such examples the need for extensive and detailed individual inquiries made the benefits of a class proceeding illusory.

Two recent decisions of the Ontario courts have changed the picture. In both Markson v. MBNA Bank Canada, 2007 ONCA 334, (leave to appeal to the Supreme Court of Canada denied November 15, 2007), and Cassano v. The Toronto-Dominion Bank, 2007 ONCA 781 the Ontario Court of Appeal has held that the Ontario Class Proceedings Act permits aggregate assessments of monetary relief, even where individual assessments would normally need to be made in order to make the substantive assessment of whether liability exists.

The limits to when a court should undertake aggregate assessments of monetary relief, as opposed to requiring individual calculations, remains to be settled. In any particular case there may be other good grounds to refuse certification of a class proceeding. But at least in Ontario, the traditional understanding of the basis for class proceedings has shifted by these recent decisions.