The provisions of Article 15 and Article 17, Paragraph 1, of the Income Tax Act as amended on January 29, 1963, requiring that a taxpayer file a joint return to include therein the income, if any, of his or her spouse and other dependents for the purpose of taxation on his or her consolidated income, are not in conflict with the Constitution insofar as the procedure of filing the return is concerned. Nevertheless, when tax is imposed on the basis of such joint return, if the tax payable by a taxpayer as computed in conjunction with the income of his or her spouse and other dependents exceeds the amount payable if it were separately computed, thereby increasing his or her taxation, the situation is contrary to the principle of fair taxation. Although such articles were partially amended on December 30, 1989, it is still advisable that review and improvements be made from time to time by competent authorities to the relevant laws by taking into consideration the social and economic conditions.

　　　 The provisions of Article 15 and Article 17, Paragraph 1, of the Income Tax Act as amended on January 29, 1963, requiring that a taxpayer file a joint return to include therein the income, if any, of his or her spouse and other dependents for the purpose of taxation on his or her consolidated income, are intended to reduce the number of tax returns to be filed and the cases of tax collection so as to save the government and the taxpayers the cost as well as the time and effort involved. The provisions are thus essential to the furtherance of the public interest insofar as the procedure of filing the return is concerned and are not in conflict with the Constitution. Nevertheless, when tax is imposed on the basis of such joint return, if the tax payable by a taxpayer as computed in conjunction with the income of his or her spouse and other dependents exceeds the amount payable if it were separately computed, thereby increasing his or her taxation, the situation is contrary to the principle of fair taxation. Although such articles were partially amended on December 30, 1989, it is still advisable that overall review and improvements be made from time to time by competent authorities to provisions related to the amounts of exemption and deduction available to such taxpayers by taking into consideration the social and economic conditions.