最高行政法院99年9月份第2次庭長法官聯席會議決議將證券投資事業之自有資金用途僅限於行為時證券投資事業管理規則第2條規定之「業務」經營之「合理必要」之用途，從而否認證券投資信託事業以自有資金承購所募集基金持有之無擔保公司債所造成的損失得以列報所得稅法第38條之投資損失。從該決議的意涵來看，似乎最高行政法院99年9月份第2次庭長法官聯席會議決議乃將所得稅法第38條的損失與費用的認列以經營本業及附屬業務的「合理及必要」的費用為限。該決議的內容已明顯增加所得稅法第38條法律所未規定的內容，而有違反租稅法律原則之虞。而所得稅法第38條營業費用的認列是否須以「合理及必要」為要件亦存有爭議之處，對此本文將從日本學說以及德國的實務及學說見解為基礎加以分析討論，並且提出個人的見解。

According to the Supreme Administrative Court's Presiding Judge's Committee September 2010 Meeting's resolution ＂Losses Incurred In The Course Of Operation Of Business Or Subsidiary Business＂ must be based on ＂reasonable＂ and ＂necessary＂ business expenses in order to be recognized as tax-deductible pursuant to art. 38 Taiwanese Income Tax Act. The Supreme Administrative Court's Presiding Judge's Committee interpretation of art. 38 Taiwanese Income Tax Act substantively alters and hampers the application of said provision by adding additional legal prerequisites not part of the language of said provision. At the same time it causes the danger to create a contradiction to fundamental and widely accepted principles of Taiwanese Income Tax Law. The comment addresses these issues and discusses them including a comparative view on German and Japanese Law.