Open Decision Ledger · Civil obligations & remedies
Set-off with an assigned claim and the date of its retroactive effect
Supreme Court, June 30, 2022, 2022Da200089 (judgment)
Case name: 정산금등청구의소
Official text on the National Law Information Center
Question
Where an assignee sets off the assigned claim as the active claim against a claim the debtor already holds against it, does the set-off take effect retroactively to the date each claim fell due, or to the date the requirements for opposing the assignment were met?
Holding
To the date the requirements were met. Article 493(2) of the Civil Act provides that a declaration of set-off extinguishes the equal amounts as at the time when set-off was possible, so its effect runs back to that moment, which arises only when the active and passive claims stand opposite each other. An assignee may exercise the assigned claim only once the requirements for opposing the assignment are met, so the effect runs back to that date and not to the maturity dates, even where both claims had already fallen due before the assignment.
Summary of the holding, verbatim
채권양수인이 양수채권을 자동채권으로 하여 그 채무자가 채권양수인에 대해 가지고 있던 기존 채권과 상계한 경우, 채권양수인은 채권양도의 대항요건이 갖추어진 때 비로소 자동채권을 행사할 수 있으므로 채권양도 전에 이미 양 채권의 변제기가 도래하였다고 하더라도 상계의 효력은 변제기로 소급하는 것이 아니라 채권양도의 대항요건이 갖추어진 시점으로 소급한다.
Unofficial English translation
Where a transferee of a claim sets off a claim it has taken by way of assignment as the active claim against a pre-existing claim that the obligor held against the transferee, the transferee may exercise the active claim only at the time when the opposability requirement (assertability against third parties) of the assignment of claim is satisfied; therefore, even though the performance dates of both claims had already arrived before the assignment of the claim, the effect of the set-off relates back not to the date of performance but to the time when the opposability requirement (assertability against third parties) of the assignment of claim was satisfied.
Disposition
Reversed and remanded Stated in the decision
원심판결을 파기하고, 사건을 서울중앙지방법원에 환송한다.
Unofficial English translation
The judgment of the court below is reversed, and the case is remanded to the Seoul Central District Court.
Form of the test
Elements stated Stated in the decision
상계적상은 자동채권과 수동채권이 상호 대립하는 때에 비로소 생긴다.
Unofficial English translation
The time when a set-off is effected arises only when the active claim and the passive claim stand against each other.
Factors
- 상계의 효력은 상계적상 시로 소급하여 발생한다.
- 상계적상은 자동채권과 수동채권이 상호 대립하는 때에 비로소 생긴다.
- 채권양수인은 채권양도의 대항요건이 갖추어진 때 비로소 자동채권을 행사할 수 있으므로
- 채권양도 전에 이미 양 채권의 변제기가 도래하였다고 하더라도
Unofficial English translation
• The effect of set-off relates back retroactively to the time when the set-off is effected.
• The time when a set-off is effected arises only when the active claim and the passive claim stand against each other.
• Since the transferee of a claim may exercise the active claim only at the time when the opposability requirement (assertability against third parties) of the assignment of claim is satisfied,
• even though the performance dates of both claims had already arrived before the assignment of the claim,
Relation to precedent
Cannot be determined Not in the decision
Decisions referred to
해당 본문 참조
Burden of proof
Not addressed Not in the decision
Open question and revisit condition
Where the debtor knew of the assignment before formal notice was given, must the set-off still be dated by the notice rather than by the knowledge?
The remand judgment of the Seoul Central District Court, once it computes both claims as of 6 July 2020, will show how the residue after the set-off is measured. A later decision on when a debtor who already knows of an assignment may set off would require this entry to be read again.
Cross-family AI independent reading & axis check
7 of 8 axes matched GPT-6 Astra (OpenAI, codex CLI) · 2026-10-25
A reader from another model family (GPT-6 Astra), given the official text but not the primary reading, agreed on 7 of the 8 axes; the readings differed on axis 8 (open question and revisit condition).
Axis 8 (Open question and revisit condition): Primary “Where the debtor knew of the assignment before formal notice was given, must the set-off still be dated by the notice rather than by the knowledge?” vs Independent “How should the effective date of setoff be determined if the validity or timing of perfection of the assignment is disputed?”
The primary reading asks whether knowledge of the assignment before notice changes the set-off date, while the independent reading asks how to fix the effective date when the validity or timing of perfection is disputed.
채권양수인이 양수채권을 자동채권으로 하여 그 채무자가 채권양수인에 대해 가지고 있던 기존 채권과 상계한 경우, 채권양수인은 채권양도의 대항요건이 갖추어진 때 비로소 자동채권을 행사할 수 있으므로 채권양도 전에 이미 양 채권의 변제기가 도래하였다고 하더라도 상계의 효력은 변제기로 소급하는 것이 아니라 채권양도의 대항요건이 갖추어진 시점으로 소급한다.Raw responses and comparison record: Protocol · Blind readings (JSONL) · Axis comparison (JSONL) · SHA-256 (JSON)
Lower-court contrast & scope of application
Lower-court reading vs. Supreme Court holding
Lower-court context: The Seoul Central District Court, in its judgment of 2 December 2021 (2020Na68907), held that the plaintiff, the issuer and manager of the T-money transport card, and SensePass obtained without legal ground the benefit of the Top T-money fares settled on Mybi's terminals, and that Mybi suffered loss of the same amount. It held that the plaintiff assumed SensePass's unjust enrichment restitution debt through the business transfer contract of 30 September 2014, and that the defendant, which Mybi had assigned the fare claim to on 7 July 2020 with notice the same day, could set off its KRW 165,323,103 restitution claim so as to extinguish the plaintiff's settlement claims in equal amounts at each maturity date, KRW 2,752,818 on 6 December 2016 and KRW 160,107,945 on 5 September 2017, leaving no settlement claim outstanding.
Supreme Court standard: The Supreme Court found no error in the findings on unjust enrichment and on the plaintiff's assumption of the restitution debt. On set-off, however, the court below premised its reasoning on the mistaken view that the due date of the original claim was the date of set-off, and simply concluded that no settlement claim remained; that misapprehended the law on the date of set-off where an assigned claim is used as the active claim and affected the judgment. Taking 6 July 2020, the day before the date of set-off, the court should have examined the principal and interest of both claims and then decided whether any settlement claim was left for the plaintiff after the set-off was applied, so the whole judgment was reversed and the case remanded to the Seoul Central District Court on the unanimous opinion of the Justices.
Distinguishing conditions
- A set-off in which neither side's claim was assigned, so that the two claims stood opposite each other at their own maturity dates and no question of a later opposition requirement arises.
- A case in which both claims had not already fallen due before the assignment, a situation this decision, framed on 'even where both claims had already fallen due before the assignment', does not resolve.
- A case in which, measured at the day before the date of set-off, the debtor's restitution claim absorbs the whole of the assignee's settlement claim and nothing is left, so the same outcome follows whichever date is used.
Record verification notes
Fix the date on which the notice of assignment gave the requirements for opposing the assignment, since the Court used 7 July 2020 for that purpose. Then take the day before that date and set out the plaintiff's settlement claim and the defendant's KRW 165,323,103 restitution claim with their amounts, due dates, periods of delay and default interest rates, because the residue after applying the set-off decides the case. Keep the findings on unjust enrichment and on the assumption of the restitution debt separate, since the Court left those undisturbed.
From the official text
Points at issue
채권양수인이 양수채권을 자동채권으로 하여 채무자가 채권양수인에 대해 가지고 있던 기존 채권과 상계한 경우, 채권양도 전에 이미 양 채권의 변제기가 도래하였더라도 상계의 효력은 변제기가 아니라 채권양도의 대항요건이 갖추어진 시점으로 소급하는지 여부(적극)
Unofficial English translation
Whether, where a transferee of a claim sets off a claim it has taken by way of assignment as the active claim against a pre-existing claim that the obligor held against the transferee, the effect of the set-off relates back not to the date of performance but to the time when the opposability requirement (assertability against third parties) of the assignment of claim was satisfied, even though the performance dates of both claims had already arrived before the assignment of the claim (affirmative)
Summary of the holding
민법 제493조 제2항은 "상계의 의사표시는 각 채무가 상계할 수 있는 때에 대등액에 관하여 소멸한 것으로 본다."라고 정하고 있으므로 상계의 효력은 상계적상 시로 소급하여 발생한다. 상계적상은 자동채권과 수동채권이 상호 대립하는 때에 비로소 생긴다. 채권양수인이 양수채권을 자동채권으로 하여 그 채무자가 채권양수인에 대해 가지고 있던 기존 채권과 상계한 경우, 채권양수인은 채권양도의 대항요건이 갖추어진 때 비로소 자동채권을 행사할 수 있으므로 채권양도 전에 이미 양 채권의 변제기가 도래하였다고 하더라도 상계의 효력은 변제기로 소급하는 것이 아니라 채권양도의 대항요건이 갖추어진 시점으로 소급한다.
Order
원심판결을 파기하고, 사건을 서울중앙지방법원에 환송한다.
Unofficial English translation
The judgment of the court below is reversed, and the case is remanded to the Seoul Central District Court.
Provisions referred to
민법 제450조 제1항, 제492조, 제493조 제2항
Read 2026-10-25 · Cross-read 2026-10-25. All quotes matched against the official text. The Chinese-character placeholders the court used for anonymised parties are given in their Korean readings, and parenthetical Chinese-character glosses are omitted.
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