Lawsuit for Return of Unjust Enrichment | Claim for Overpaid Construction Costs, Full Payment Awarded

Unjust enrichment refers to a benefit obtained by an improper means that violates the law.

If, for some reason, a person acquires another person's property or labor but has no legal entitlement to the benefit and must return it, the benefit so obtained is unjust enrichment.

The Civil Act provides that a person who obtains a benefit from another's property or services without a legal cause, causing loss to that other person, shall return the benefit.

The client originally subcontracted the construction work in this case, worth about 1 billion won, from A Construction.

Afterward, the client and A Construction amended the contract a total of three times, changing the construction amount due to issues such as added volume.

After concluding the subcontract with A Construction, the client entered into a sub-subcontract agreement with the defendant.

The settlement agreement between the client and the defendant specified that progress payments would be made to the defendant after deducting 10% (office operating expenses) from the amount deposited following the issuance of the invoice.

The defendant, however, argues that it agreed to deduct the 10% office operating expenses only with respect to the initial construction amount of 1 billion won for this case, and that it never agreed to pay the same amount with respect to the construction amounts that were subsequently changed and increased.

The attorney handling the client's lawsuit for the return of unjust enrichment rebutted the defendant's argument by pointing out that, although the construction amount was changed several times between the plaintiff and A Construction, no separate contract was prepared between the plaintiff and the defendant on each such occasion, and that the 10% the plaintiff agreed to deduct meant 10% of the total construction progress payments.

The attorney handling the lawsuit for the return of unjust enrichment pointed out that there was no evidence whatsoever to prove the defendant's claim that the plaintiff had agreed not to receive a fee on the additional construction work.

The attorney handling the lawsuit for the return of unjust enrichment emphasized that not only was there no evidence whatsoever to prove it, but it also ran contrary to ordinary contracting practice and therefore lacked any credibility.

The progress amount is about 1 billion won, and the amount after deducting 10% from that progress amount is 900 million won.

Because the amount the plaintiff prepaid to the defendant came to about 1 billion won, the plaintiff overpaid the defendant by 100 million won.

The attorney handling the lawsuit for the return of unjust enrichment argued that the defendant has a duty to return to the plaintiff the 100 million won overpaid, together with the delay damages thereon.