The provisions of Article 65, paragraph (1), Article 66, paragraph (1), and Article 68, paragraphs (1) and (2) of the Act on General Rules for National Taxes as amended by the provisions of Article 8 (hereinafter referred to as "the new Act on General Rules for National Taxes" in this Article) apply to national tax whose statutory tax return due date as prescribed in Article 2, item (vii) of the new Act on General Rules for National Taxes (including a due date deemed to be that statutory tax return due date under the provisions of the national tax laws, and, for a return of refund claim as prescribed in Article 61, paragraph (1), item (ii) of the new Act on General Rules for National Taxes, meaning the day on which that return was filed; hereinafter referred to as the "statutory tax return due date" in this Article) arrives on or after October 1, 1987, and with regard to the imposition of penalty tax for understatement, penalty tax for failure to file, and heavy penalty tax on national tax whose statutory tax return due date arrived before October 1 of the same year, the provisions then in force continue to govern.