638.No tax is payable in respect of the consideration that was paid or became due before 1 November 1992 for the supply of a service in respect of which tax under Chapter II of the Retail Sales Tax Act (chapter I-1) does not apply if all or substantially all of the service was not performed before 1 July 1992, to the extent that the consideration relates to any part of the service that was performed before 1 July 1992.