세법상 신뢰보호 원칙의 해석 -대법원 2023. 12. 7. 선고 2020두42668 판결의 평석을 중심으로-

The “principle of trust protection(Estoppel)” is a fundamental aspect of constitutional law, ensuring citizens’ assertiveness in the predictability and reliability of government actions, thereby upholding the principles of a rule of law and legal stability. When confronted with amendments to tax laws that may adversely affect taxpayers, the judiciary, particularly the Constitutional Court and the Supreme Court, play a pivotal role in interpreting and applying the principle of trust protection as enshrined in constitutional, administrative, and tax laws. While there may be variations or adjustments in the specific criteria emphasized in judiciary precedents, the overarching jurisprudence remains consistent; to ascertain the presence of trustworthiness in the beliefs of taxpayers, determining whether there exists substantial reliance by taxpayers on the previous tax laws and assessing the balance of interests between the trust of taxpayers vested in previous rules and the public welfare pursued by recent one. In cases where the principle of trust protection in tax laws is challenged, the Supreme Court meticulously examines whether statutory provisions explicitly safeguard taxpayers’ trust in advantageous provisions of previous tax regulations. Notably, if such explicit provisions are found within the previous one, the Court acknowledges the value of protecting taxpayers’ reliance on those laws. In the same vein, recent judicial decisions have punctuated the importance of explicit statutory in conferring protection on taxpayers’ trust, highlighting that mere expectations without explicit provisions may not warrant significant protection. However, the Court need to consider the interpretative scope of previous laws and their impact on taxpayers’ trust, moving beyond formalistic criteria as used it above, to evaluate the substantive implications on the range of trust vested in taxpayers. In terms of material criteria favoring taxpayers’ trust, which are related to the tax liability and vested into the previous laws, it should be acknowledged as a worthy of safeguarding, given its implications for taxpayers’ assertion in the legal system. Nevertheless, even following with such recognition, the courts face challenges in prioritizing taxpayer trust over the broader public interest, particularly in the context of tax law where considerations of public welfare often prevail. Therefore, while the principle of trust protection remains integral to legal interpretation and application, determining its applicability requires a careful balance between safeguarding taxpayer trust and upholding the broader objectives of public policy within the framework of tax laws.