(b) Municipal Ordinance to be applied before and after the amendment, in cases where the Municipal Ordinance concerning taxation or exemption of the market price has been amended;

(c) Criteria for determining whether any defect in filing a tax return by a method of tax return corresponds to the invalidation thereof, because it is grave and obvious;

(d) The case holding that an act of voluntary declaration and payment of acquisition tax falls under the invalidation thereof as it has a significant and obvious defect;

E. Whether the Civil Act applies to unjust enrichment arising from tax law relations

B. In the case of the amendment of the Municipal Ordinance on Taxation or Exemption of Market Price, the pertinent Municipal Ordinance that was enforced at the time of the establishment of tax liability among the ordinances before and after the amendment shall be governed by the principle of no payment in law. However, in the case of the amendment of the Municipal Ordinance disadvantageously, in a case where the previous Municipal Ordinance, which was enacted in order to protect the taxpayer’s rights and trust, requires the taxpayer to apply the previous Municipal Ordinance

C. Acquisition tax and registration tax are taxes in the form of tax return, in principle, the tax liability is determined specifically by the taxpayer's act of setting his tax base and amount of tax and filing a return (limited to the case where the tax office does not file a return from the taxpayer), and its payment is the performance of specific tax liability confirmed by the return, and the State or a local government holds the tax amount paid based on the final tax claim as above. Thus, unless the taxpayer's act of filing a return is null and void as a result of a serious and obvious defect, it shall not be deemed as unjust enrichment. Here, as to whether the act of filing a return constitutes null and void as a matter of course due to a significant and apparent defect, the purpose, meaning, function, and legal remedy, etc. of the act of filing a return shall be considered as the basis for the act of filing a return, and it shall be reasonably determined by the specific circumstances caused by the act of filing a return.

(d) The case holding that if the taxpayer's voluntary declaration prior to the payment of the acquisition tax is an object of exemption under a municipal ordinance and the tax authority applied for exemption, but the taxpayer's voluntary declaration and payment is inevitable due to the tax evasion due to neglect of voluntary declaration and payment and the necessity of prompt preservation of ownership, and the taxpayer's claim for the return of the above amount of tax by civil procedure was caused by the remedy, the above filing act constitutes a substantial and obvious defect that has no room for recognizing the ability to establish the tax liability due to such special circumstance.

E. With respect to unjust enrichment arising from a tax law relationship between a taxpayer and a tax authority, the provisions of civil law shall not apply.

The costs of appeal shall be assessed against each appellant.

As to the Plaintiff’s ground of appeal

The amount of education tax added to the amount of registration tax, which is a local tax, shall be imposed and collected by the head of a Si/Gun or a public official delegated by him/her (Article 10(4) of the Education Tax Act). Since the education tax collected by a local government is to be paid to the National Treasury (Article 10(1) and (2) of the Enforcement Decree of the Education Tax Act), a claim for unjust enrichment on the education tax paid in addition to the registration tax voluntarily reported and paid, shall be made against the National Treasury that is the subject of benefit (see, e.g., Supreme Court Decisions 87Meu317, Feb. 14, 1989; 94Da10740, Sept. 27, 1994); and there is no reason

As to the Defendant’s ground of appeal

1. As to the first to seventh points

According to the reasoning of the judgment below, the court below acknowledged that the plaintiff constructed a building for the business facilities of this case with the approval of an urban redevelopment project for urban redevelopment project under the Urban Redevelopment Act on June 27, 1989 and completed the completion inspection on June 19, 1993, the acquisition tax and registration tax shall be exempted on July 19, 1993, and the acquisition tax shall be 408,083,780, and the registration tax shall be 16,23,510, and the registration tax shall be 16,23,510, etc. on August 12, 1993, and in this case, the plaintiff shall be exempted from the acquisition tax and registration tax since the Ordinance on Tax Exemption for Urban Redevelopment Project under the Urban Redevelopment Act was applied to the plaintiff at the time of the execution of the above project in favor of the plaintiff, and therefore, the defendant shall return the above acquisition tax

In the case of the amendment of the Municipal Ordinance on Taxation or Exemption of Market Price, the term "the Municipal Ordinance to be implemented at the time when the liability for tax payment was established" shall be natural in light of the principle of no taxation in law. However, in the case of the amendment of the Municipal Ordinance disadvantageously, if the previous Municipal Ordinance to be applied to taxpayers with special transitional provisions for the benefit of persons liable for tax payment or for the protection of trust, the previous Municipal Ordinance should be applied (see, e.g., Supreme Court Decision 87Nu8, May 12, 1987; Supreme Court Decision 89Nu468, Apr. 10, 199; Supreme Court Decision 93Nu15649, Dec. 28, 1993).

In the same purport, the court below has no reason to hold that the building of this case is subject to exemption from acquisition tax and registration tax by applying the Municipal Ordinance at the time of authorization for project implementation, not the Municipal Ordinance at the time of completion and registration of preservation of ownership, pursuant to Article 2 of the Addenda to the Seoul Metropolitan Government Ordinance on Exemption from Taxation (Municipal Ordinance No. 2843), which was amended after authorization for project implementation for a building due to urban redevelopment project of this case after authorization for the implementation of the urban redevelopment project of this case, and there is no reason to view that the building of this case is subject to exemption from acquisition tax and registration tax by applying

In addition, Article 4 (1) of the above Ordinance provides that a person who wishes to be exempted from taxation shall file an application with the head of the competent authority along with a document proving the fact. However, the above provision on the application for exemption is merely a provision on the procedures for handling affairs for the convenience of handling exemption, but it cannot be deemed that the application is a requirement for exemption. Therefore, no other discussion

However, the acquisition tax and registration tax are taxes in the form of tax return and payment, in principle, the tax liability is specifically determined by the taxpayer's act of determining his tax base and amount of tax (limited to the case where the tax office does not file a return from the taxpayer) and its payment is the performance of specific tax liability confirmed by the tax return, and the State or a local government holds the tax amount paid based on such determined tax claim. Thus, unless the taxpayer's act of filing a return is void automatically due to a grave and obvious defect, it shall not be deemed as unjust enrichment immediately. Here, as to whether the act of filing a return constitutes void automatically due to a grave and obvious defect, the purpose, meaning, function, and legal remedy for the act of filing a return at the same time shall be examined and determined on an individual basis (see, e.g., Supreme Court Decision 86Nu112, Sep. 23, 1986; Supreme Court Decision 90Meu1086, Nov. 27, 1990; Supreme Court Decision 200Nu31394, Nov. 13, 194).

However, according to the records, the plaintiff asserted that the acquisition tax is subject to exemption under the ordinances before the voluntary report payment in this case, and applied for exemption to the defendant. However, the defendant did not comply with the repeated opinion of the party members as seen earlier, and as a result, the plaintiff's refusal of exemption is inevitable voluntary report and payment due to the necessity of avoidance of additional tax due to failure to pay voluntary report and prompt preservation of ownership, and the relief method by administrative litigation is not acknowledged as the remedy of this case (see Supreme Court Decision 88Nu3406, Dec. 20, 198; Supreme Court Decision 88Nu3406, Dec. 20, 198; Supreme Court Decision 88Nu3406, Dec. 20, 198). Accordingly, in this case, the defendant has no room for recognizing the ability to confirm the above tax obligation due to such special circumstances, and therefore, the defendant has no legal ground for the payment of the tax amount, and thus, the court below's decision that recognized unjust enrichment against the defendant is justified.

2. On the eighth ground for appeal

Since the provision of the Civil Act does not apply to unjust enrichment arising from a tax law relationship between a taxpayer and a tax authority (see, e.g., Supreme Court Decision 87Meu2569, Jan. 25, 191), the argument is without merit.

Therefore, both appeals are dismissed. The costs of appeal are assessed against each appellant. It is so decided as per Disposition by the assent of all participating Justices on the bench.

Justices Kim Jong-soo (Presiding Justice)