本文評析大法官釋字第650號解釋及大法官釋字第657號解釋。釋650處理「81年修正之營所稅查核準則第36條之1第2項是否違憲？」之爭議，而釋657則解釋「所得稅法細則第82條第3項、營利事業所得稅查核準則第108條之1是否合憲？」之爭議。本文認同釋650之解釋，「稽徵機關…得就公司資金貸與股東或他人而未收取利息等情形，逕予設算利息收入，課徵營利事業所得稅。上開規定欠缺所得稅法之明確授權，增加納稅義務人法律所無之租稅義務，與憲法第十九條規定之意旨不符，應自本解釋公布之日起失其效力。」但基於公平課稅原則，本文不認同釋657解釋「關於營利事業應將帳載逾二年仍未給付之應付費用轉列其他收入，增加營利事業當年度之所得及應納稅額，顯非執行法律之細節性或技術性事項，且逾越所得稅法之授權，違反憲法第十九條租稅法律主義，應自本解釋公布之日起至遲於一年內失其效力。」文中說明同意與不同意之理由，並提供相關之建議 This paper discusses the J.Y Interpretation 650 and the J.Y Interpretation 657. The Interpretation 650 examines the issue “Are Article 82, Paragraph 3 of the Enforcement Rules of the Income Tax Act and Article 108-1 of the Guidelines for the Audit of Income Taxes on Profit-seeking-enterprises constitutional?” The Interpretation 657 examines the issue “Are Article 82, Paragraph 3 of the Enforcement Rules of the Income Tax Act and Article 108-1 of the Guidelines for the Audit of Income Taxes on Profit-seeking-enterprises constitutional?” This paper has the same opinion on The Interpretation 650 which holds that “The tax collection authority summarily levies taxes over interest income based on this rule on company loans to its shareholders or other persons. Since such regulation lacks clear and specific authorization from the Income Tax Act, increases the tax obligation which does not legally exist for tax payers, and contradicts the meaning and purpose of Article 19 of the Constitution, it shall be invalid as of the date this Interpretation is issued.” And this paper has the different opinion on The Interpretation 657 which holds that “ That profit-seeking enterprises shall convert and list unpaid expenses or losses having exceeded two years from account payables to the heading of other revenues under the above-stated regulations so that the income and taxable revenue of that enterprise is increased for the year is obviously not a detailed or technical enforcement issue, and has usurped the authorization of the Income Tax Act, thereby violating the principle of taxation by law under Article 19 of the Constitution. The provisions in question should be invalidated no more than one year since the issuance of this Interpretation.” based on the right of equal protection as stipulated in Article 7. This paper provides the why and the how on the two issues.