The provisions of Article 23, paragraph (1) of the Act on General Rules for National Taxes as amended by the provisions of Article 17 (hereinafter referred to as "the new Act on General Rules for National Taxes") apply to national tax for which the statutory tax return due date prescribed in that paragraph arrives on or after the effective date, and the provisions then in force continue to govern national tax for which the statutory tax return due date prescribed in Article 23, paragraph (1) of the Act on General Rules for National Taxes prior to the amendment by the provisions of Article 17 (hereinafter referred to as "the former Act on General Rules for National Taxes") arrived before the effective date.