「經濟實質原則」（Economic Substance Doctrine）美國稅法領域中最著名的司法原則（Judicial Doctrine）之一。自一九三五年聯邦最高法院宣判Helvering v. Gregory 案以來，經濟實質原則成為法院用以否決納稅義務人的無實質經濟效果交易、卻主張有減免稅賦權利之稅務案件。雖然經濟實質原則影響稅法達七十五年之久，但畢竟還是「司法造法」下的產物，並非是經過國會所通過的成文法。蓋因法院對經濟實質原則要件及適用標準見解歧異，且在最高法院傾向原文主義之風氣下，國會擔心有朝一日經濟實質原則會被廢止，遂於二○一○年將爭議多年的經濟實質原則藉由通過「保健暨教育法案」（Health Care and Education Reconciliation Act of 2010）時增訂I.R.C. §7701(o)予以成文法化，明確規範之，以期終結法院在解釋經濟實質原則時不同見解之混亂，並將經濟實質原則「妾身不明」之疑慮一併消除，就地「合法化」。對於已習慣判例法下經濟實質原則的納稅義務人、國稅局及法院，成文法化將對三方產生重大的變化。I.R.C. §7701(o)將對未來稅務實務發展產生重大之影響。經濟實質原則成文法化是利是弊，尚待時間考驗；惟毫無疑問的是，經濟實質原則成文法化將納稅義務人、政府及法院三方推向另一個層次的競技場。

The economic substance doctrine is one of the most famous judicial doctrines in the area of tax law. Since Helvering v. Gregory (1935), courts have been applying the economic substance doctrine to disallow the tax benefits generated by transactions that had no effect on the economic position of the taxpayers. Although, the economic substance doctrine has a great impact in the area of tax law, it is still a "judicially crafted doctrine", not the law passed by Congress.Courts are split on the application of the economic substance doctrine. Furthermore, the Supreme Court has grown increasingly in favor of textualism, Congress was worried that the Supreme Court may overrule the economic substance doctrine. Therefore, Congress, as part of the Health Care and Education Reconciliation Act of 2010, codified the economic substance doctrine as new code section I.R.C. §7701(o). The codification of the economic substance doctrine clarifies its application which has been applied by courts for many years. However, for taxpayers, the Internal Revenue Service and courts, the codification may bring many challenges.I.R.C. §7701(o) will have a great impact in the area of tax law. Only time will tell how good or bad this new section was. However, without a doubt, the codification will push taxpayers, the Internal Revenue Service and courts to another level.