639. Subject to section 647, consideration for the taxable supply of a service, other than a transportation service, in respect of which tax under Chapter II of the Retail Sales Tax Act (chapter I-1) does not apply is deemed to have become due on 1 July 1992 and not to have been paid before 1 July 1992 if the consideration was paid or became due after 30 April 1992 and before 1 July 1992.