[2] In a case where multiple automatic claims exist and the principal and interest of multiple claims fall short of the total sum of the principal and interest of automatic claims, the method of offsetting or appropriation

[3] In a case where a set-off claim with multiple automatic claims has grounds, the court shall enter the scope of res judicata effect of the set-off in the grounds for judgment

[4] In a case where Gap sought the performance of the contract deposit claim against Eul, and Eul made a set-off claim against Eul by using the damage claim or the claim for return of unjust enrichment against Eul as the automatic claim, the case holding that the court below erred in the misapprehension of legal principles as to the res judicata effect of set-off or the appropriation of set-off in the reasoning of judgment without mentioning the original and the damages for delay among the damage claim or the claim for return of unjust enrichment, which is the automatic claim of set-off, as the counterclaim of set-off in the ground of judgment, and the initial date and interest rate of the extinguished damages for delay,

In the event of declaration of intention of offset, the obligation is deemed to be extinguished on an equal amount retroactively from the time of offset. As such, calculation of the difference between the two claims by offset or appropriation of offset shall be based on the time of offset. Therefore, in case where delay occurs due to the arrival of the time of repayment of the passive claim prior to that time, then calculating the parties to the agreement on the passive claim and the damages for delay as of the time of offset, the parties to the agreement and the damages for delay should be calculated, and then the original claim should be retired with the balance (see Supreme Court Decision 2005Da8125, Jul. 8, 2005, etc.).

Meanwhile, in the case of a set-off, the legal doctrine of appropriation of performance under Articles 476 and 477 of the Civil Act is applied mutatis mutandis in accordance with Article 499 of the Civil Act. Accordingly, in a case where several automatic claims exist and the principal and interest of several claims fall short of the total sum of principal and interest of the claims, the obligee of the automatic claim may designate the automatic claim subject to a set-off, and thereafter, the obligor of the automatic claim may designate it, and if both parties do not designate it, the set-off appropriation is made by means

However, the res judicata effect takes effect on the amount set up against a set-off regardless of whether it is accepted or not (Article 216(2) of the Civil Procedure Act). Therefore, in cases where several automatic claims exist, the court should clarify the grounds for the judgment whether to effect res judicata on any of them within the scope of offset against one of them in itself or to the extent that the parties can clearly understand the grounds for the judgment. Therefore, where there are grounds for a set-off defense, even if the amount of the claim to be extinguished by the set-off is not calculated daily, it should clarify whether at least the set-off appropriation would be based on the designated appropriation or legal appropriation, and if the designated appropriation would be made, what kind of automatic claim should be first appropriated, and if interest or late payment damages are claimed with the automatic bond, the court should specify the date and interest rate in detail.

In this case, the court below first determined that the defendant is liable to pay the plaintiff 16,600,000 won and damages for delay on the ground of the agreement in this case. Further, the defendant's defense that the plaintiff set off the claim for damages or the claim for return of unjust enrichment against the plaintiff as an automatic claim on an equal amount with the plaintiff's claim for reimbursement of unjust enrichment shall be based on the facts acknowledged by the adopted evidence, and the plaintiff is liable to pay the plaintiff 72,000 won and the damages for delay, and the damages for delay shall be KRW 18,60,000 and the damages for delay shall be paid to the defendant as compensation or return of unjust enrichment. The plaintiff's claim in this case against the defendant was set off on April 30, 200, which was set off on the same day as the date when the final payment period of the claim in this case reaches the due date, and thus, the court below erred by misapprehending the legal principles as to the plaintiff's claim for compensation for unjust enrichment or its damages within the scope of set-off or set-off damages.

Therefore, without further proceeding to decide on the remaining grounds of appeal, the lower judgment is reversed, and the case is remanded to the lower court for further proceedings consistent with this Opinion. It is so decided as per Disposition by the assent of all participating Justices on the bench.

Justices Cha Han-sung (Presiding Justice)