摘要
稅捐稽徵法第11條之6制定通過後，稅捐法上已經確立了證據禁止理論之適用，然而，單一條文無法適用於所有證據禁止之案型。由於本文認為稅捐法上之證據禁止理論，其功能與適用與刑事訴訟類似，刑事追訴不允許國家不計代價地去取得證據、發現真實，同理，稅捐法上也不應允許不擇手段地調查與取得證據，稅捐證據之調查應有所節制，必須遵守法定程序以及比例原則。因此本文參考刑事法上之證據禁止理論以及德國文獻，補充提出可能之操作模式。 本文將違法取證之結果，分為三種情形：證據必須絕對禁止使用、證據不會禁止使用，以及由法院權衡判斷應否禁止使用。取得證據之程序雖有違法，但並非全然招致證據禁止使用之結果。 機關合法取證或私人不法取證，並非機關違法取證，原則上不招致證據禁止之結果。但若係以嚴重侵害基本權之方法取證，或使用證據係嚴重侵害基本權者，例如侵害私人之人性尊嚴或私人生活隱私領域等，證據應禁止使用。訴訟上之調查證據程序瑕疵，尚不致證據禁止，但可能有於法庭重新調查之必要。 再者，縱然有證據禁止使用之情形，並不代表系爭行政處分絕對有實體上之瑕疵，當某項證據被禁止使用，卻沒有其他證據足以認定事實，或其他證據無法處分所憑據之事實（其他證據之證明力不足），或機關未調查及採納其他證據，此些情形下，才可謂行政機關對事實認定有誤，所作成之實體決定罹有瑕疵。
並列摘要
Government agencies shouldn’t obtain evidence by all means or ascertain the truth at all costs, in both Criminal Procedure and Tax collecting Procedure. The Principle of Proportionality should be applied while tax investigation and evidence obtaining. Article 11-6 of Tax Collection Act provides: “A confession unduly obtained by a tax collection authority and in violation of the fact shall not be presented as evidence for assessment or punishment.” Since Article 11-6 of Tax Collection Act has taken effect, the Exclusionary Rule has also been established in Tax Law. However, Art. 11-6 of Tax Collection Act is the only and single provision related to The Exclusionary Rule in Tax Law. In other words, the single provision, Art. 11-6 of Tax Collection Act, couldn’t be applied to every situation of illegally obtaining evidence. Therefore, why and how the Exclusionary Rule is operated and applied in Tax Law are indicated in this study which refers to the theories of the Exclusionary Rule in the Code of Criminal Procedure and also introduces the theories of the Exclusionary Rule in the German Tax Law. Depends on how serious the unlawful behavior is, the illegally gathered evidence by the authority would lead to admissibility, mandatory exclusion or deciding whether or not to exclude evidence by court through weighing and balancing multiple factors to decide cases where constitutionally protected individual rights conflict with governmental interests. The evidence obtained illegally by private individuals or obtained legally by the authority is basically admissible. Nevertheless, the evidence is not admissible if private individuals infringe others’ human dignity or seriously infringe others’ fundamental rights while obtaining the evidence. If the use of evidence would seriously infringe others’ basic right such as sacrosanct private sphere or human dignity, those evidences should be forbidden even they were gathered legally by the authority. The illegally obtained evidence is not necessarily excluded. Furthermore, the evidence is excluded doesn’t mean that the administrative disposition is absolute void. If there is no other evidence exist or other evidence couldn’t prove the truth when the illegal collected evidence is excluded, the substantive decision is unlawful and could be withdrawn.