the amount obtained by deducting, from the amount of income tax on the person's taxable gross income for 1976 (if the Income in Each Class that served as the basis for calculating that taxable gross income included capital gains, occasional income, miscellaneous income or Ad Hoc Income not falling under miscellaneous income, the amount calculated by deeming those amounts not to have existed in accordance with the provisions of the Cabinet Order under Article 104, paragraph (1), item (i) of the Income Tax Act prior to amendment (hereinafter referred to as "the former Act"), and, if the provisions of Article 2 (Reduction of or Exemption from Income Tax) of the Act on Reduction or Release, Deferment of Collection and Other Measures Related to Tax Imposed on Disaster Victims (Act No. 175 of 1947) applied to income tax for that year, the amount calculated as if the provisions of that Article had not applied), the amount of income tax that was or should have been collected through withholding from Each Class of Income concerned (excluding the amount relating to occasional income, miscellaneous income and Ad Hoc Income not falling under miscellaneous income);