12. In the case of a trust scheme (whether or not a money purchase scheme) which apart from this regulation could not be modified for the purpose of making provision for the total amount of a debt due under Article 75(1) to be apportioned amongst the employers in different proportions from those which would otherwise apply by virtue of Article 75(1A) (as inserted by regulation 4(2) or, as the case may be, regulation 8), for the purposes of Article 68(2)(e), such a modification of the scheme is a modification for a prescribed purpose.