由於網際網路的全球化，21世紀的商業活動原本就不以在所得來源國成立「常設機構」為必要，因而對於國際間課稅管轄權的分配規則有所衝擊。其中，引起輿論多所關注者，莫過於是我國境內營業人在「臉書」（Facebook）上購買廣告時，是否應為境外的臉書公司代為扣繳稅捐？該案所引發的稅務訴訟，雖然最後由最高行政法院一○九年度上字第九七二號判決畫下休止符，但該號判決所引發的諸多議題，例如：臉書提供網路投放廣告服務獲取的報酬是否確為臉書的營業利潤？又現制下對於跨境電商課徵所得稅的規範位階是否足夠？以及對於我國境內營業人課予扣繳義務是否合理？這些問題，不論是在解釋論或立法論層次的討論，似乎未因判決的作成而定紛止爭。本文對此將分別評析，並提出不同的觀察視角。

Due to the globalization of the Internet, “Permanent Establishment” was originally unnecessary in the country of origin of income source for commercial activities in the 21st century. As a result, certain impacts have been ensued on the distributive rules of international tax jurisdiction. Among them, whether Taiwan’s local business entities should withhold taxes for the overseas Facebook Company when purchasing advertisements on Facebook has attracted considerable attention. Although the tax lawsuit triggered by aforesaid case was finalized based on the Shang-Zi No. 972 Judgment of the Supreme Administrative Court in 2020, this judgment sparked many issues. For example, whether the remunerations obtained by Facebook from online advertisement placement services can be confirmed as business profits of Facebook? Are the legal norm hierarchies established for collecting income tax from cross-border e-commerce under the current system sufficient? And is it reasonable to impose a tax withholding obligation on the business entities in Taiwan? The discussion of these questions at the level of interpretative theory or legislative theory has not yet been undisputed due to the conclusion of the aforesaid court judgment. Therefore, this article will evaluate and analyze such issues as well as put forward different observational perspectives.