租稅規避為造成我國稅基侵蝕的主因之一，企業大股東進行租稅規避時更會造成鉅額稅收損失，所得稅法第66條之8乃我國防杜股權不當避稅的主要規定，然而實務上卻造成徵納雙方重大衝突，引起實質課稅原則是否違背租稅法定主義的爭論，據此，所得稅法第66條之8在學理及實務運用上仍存在深入探究之價值。
本文彙總整理94年至105年訴願決定書與高等行政法院裁判書相關案例，以個案分析方式將避稅態樣分類、歸納徵納雙方的爭點和法院裁定及提出政策修法方向，研究結果顯示證券交易所得免稅是造成此種避稅態樣浮濫的主因，現行法律條文對於此種避稅要件的規定過於抽象，裁罰要件的規定也不夠明確，未來修法應將解釋函令規範要件納入母法及明定裁罰要件，以符合租稅法定主義，真正落實實質課稅精神。

It is tax avoidance that causes tax base erosion in Taiwan. Tax avoidance cited by major shareholders in gargantuan businesses damages the tax revenue even more seriously. Although Article 66-8 of Income Tax Act is the main weapon fighting tax aggressiveness in illegally shifting share ownership, the provision causes great conflicts between tax payers and tax authorities, disputing about whether the Principle of Substantive Taxation violates the Principle of Taxation under the Law. Therefore, how Article 66-8 of Income Tax Act works has much to be dug both theoretically and pragmatically.
This paper summarizes cases involving Article 66-8 of Income Tax Act in administrative Appeal Decisions on Ministry of Finance and final judgments on High Administrative Courts from year 2005 to 2016. By case studying, this paper not only classifies but files out some arguing points and the judgment rendered by the court to point out how the Act should be revised. This research concludes that the blooming tax avoidance cases are due to exemption from gains derived from the securities transactions. The conclusion also points out that current legal provisions are ambiguous on both imposition and penalty factors .In order to carry out the Principle of Substantive Taxation and the Principle of Taxation under the Law, legisltors must put the imposition and penalty factors into the provision when enacting tax reform bill in the future.

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Myron S Scholes, Mark A. Wolfson , Merle M. Erickson , Michelle L. Hanlon , Edward L. Maydew Terrence J. Shevlin 2015. Taxes and Business Strategy, Fifth Edition