1. Acquisition tax is a tax by self-return, in principle, a taxpayer's tax base and amount of tax are determined by the act of filing a return, specifically determining the tax base and amount of tax and the act of filing a return is the performance of specific tax liability established by the return, and local governments hold the tax amount paid based on the final tax claim as such. In principle, in order to make such a taxpayer's act of filing a return to be null and void as a matter of course, the defect must be significant and apparent. Here, as to whether the act of filing a return constitutes void as a matter of course because of a significant and apparent defect, the purpose, meaning, function, and legal remedies for the act of filing a return should be considered as a basis for the act of filing a return, and it should be reasonably determined by individually and reasonably by considering the specific circumstances arising from the act of filing a return (see Supreme Court Decisions 94Da31419, Feb. 28, 1995; 204Da64340, Jan. 13, 2006

However, the act of reporting acquisition tax is conducted between a taxpayer and a tax authority, and the protection of a third party trusting the existence of acquisition tax is not particularly problematic, and even if the act of reporting is null and void, it does not seriously undermine legal stability. However, even if there are serious defects in taxation requirements, etc., and the legal remedies are relatively insufficient compared with national taxes, and it is reasonable to exceptionally consider the stability of tax administration and the request for smooth operation thereof, if there are special circumstances to deem that the act of reporting is considerably unreasonable from the perspective of protecting rights and interests of a taxpayer even if considering the stability of tax administration and the request for smooth operation thereof.

2. According to the reasoning of the judgment below, the court below held that the Plaintiff’s voluntary declaration of the acquisition tax, etc. on the instant real estate on December 16, 1999 (hereinafter “instant declaration”), and that even though the Defendant notified the Plaintiff of the payment of acquisition tax, etc. on May 16, 200 and April 1, 2003, the Plaintiff did not appeal the tax authority, etc. on the ground of the defect in the instant declaration act until filing the instant lawsuit, it cannot be deemed that the defect in the instant declaration act is evident, and thus, the instant declaration act cannot be deemed as null and void as a matter of course.

3. However, the following circumstances revealed by the reasoning of the judgment below and the record, namely, in the case of the instant declaration act with respect to acquisition tax, etc., it seems that the protection of a third party trusted the existence thereof is not particularly problematic, and even if such declaration act is null and void automatically, it would not seriously undermine legal stability. The Plaintiff not only failed to meet the formal requirements for acquiring ownership, such as registration, but also appears to have enjoyed profits, etc. based on the acquisition of the instant real estate as the Plaintiff failed to meet the substantive requirements for acquiring ownership, such as the payment of the price, and there are serious defects such as not meeting the taxation requirements for acquiring the instant real estate, and even if the legal remedies are relatively insufficient compared to the national tax, it seems that imposing disadvantages on the Plaintiff due to the instant declaration act is remarkably unfair from the perspective of remedy for rights and interests of the Plaintiff. Even if the instant declaration act is null and void automatically, it is difficult to conclude that it impedes the smooth operation of the taxation administration. Thus, there are special circumstances to deem such defect to be null and void.

Nevertheless, the court below determined otherwise that the act of reporting in this case cannot be seen as abrupt invalidation. In so doing, the court below erred by misapprehending the legal principles as to the invalidation of abrupt invalidation of acquisition tax return, thereby adversely affecting the conclusion of the judgment.

4. Therefore, the lower judgment is reversed, and the case is remanded to the lower court for a new trial and determination. It is so decided as per Disposition by the assent of all participating Justices on the bench.

Justices Yang Chang-soo (Presiding Justice)