All appeals are dismissed.

The costs of appeal are assessed against the plaintiffs.

The grounds of appeal are examined.

As a matter of principle, the tax by the method of tax return is determined by the taxpayer's own determination of the tax base and the amount of tax, and the payment is determined by the specific tax liability determined by the return, and the State and local governments hold the tax amount paid based on the finalized tax claim.

Unless a taxpayer's filing of a return is void as a result of significant and apparent defects, it shall not be deemed as unjust enrichment.

Here, whether a defect in the act of reporting constitutes the invalidity of the law because it is significant and clear should be determined reasonably by considering the purpose, meaning, function, and legal remedies for defective act of reporting as a basis for the act of reporting from a teleological perspective, and by individually identifying specific circumstances caused by the act of reporting.

(see, e.g., Supreme Court Decisions 94Da60363, Dec. 5, 1995; 2006Da81257, Apr. 23, 2009). The lower court partially citing the reasoning of the first instance judgment and, in addition to the reasons indicated in its reasoning, rejected all the Plaintiffs’ claims on the grounds that the act of return and payment in this case cannot be deemed as null and void as it is difficult to deem that there is a serious and obvious defect.

Examining the records in light of the aforementioned legal principles, the above determination by the court below is just, and contrary to the allegations in the grounds of appeal, there were no errors in the misapprehension of legal principles as to the invalidity of a report

Therefore, all appeals are dismissed, and the costs of appeal are assessed against the losing party. It is so decided as per Disposition by the assent of all participating Justices on the bench.