1. The Plaintiff (Counterclaim Defendant) paid KRW 425,689,00 to the Defendant (Counterclaim Plaintiff) for KRW 425,689,00 and the Plaintiff’s payment thereof from July 7, 2016 to December 14, 2017.

Basic Facts

The relevant Plaintiff (formerly: Changdae L&C Co., Ltd.) is a company that carries on the construction business of water supply and drainage facilities, and the Defendant is an association established pursuant to the Act on the Maintenance and Improvement of Urban Areas and Dwelling Conditions for Residents (hereinafter “Urban Improvement Act”) to carry on the redevelopment project of housing in Seongdong-gu Seoul Metropolitan Government B (hereinafter “instant project zone”).

The Plaintiff entered into each of the instant sewerage construction contracts with the Defendant for the following four contracts regarding the sewerage construction works within the instant project area (hereinafter “each of the instant sewerage construction contracts”).

On July 6, 2010, the Plaintiff entered into a contract under which the Defendant would receive a contract for the sewerage construction work within the instant business area (hereinafter “the main construction contract”) with the amount of construction cost of KRW 981,00,000 (excluding value-added tax; hereinafter the same shall apply). Of the above payments, the down payment is KRW 392,40,000, the intermediate payment is KRW 294,300,000, and the remainder is KRW 294,30,000, and the intermediate payment is paid according to the process, and the remainder is paid within 20 days after the completion of construction.

On June 29, 2012, the Plaintiff entered into a contract with the Defendant to pay KRW 790,000,000 for the additional construction works for the diameter change section in the instant project zone, and entered into a contract with the Defendant on December 10, 2012, changing the said construction cost to KRW 871,00,000 (hereinafter referred to as “additional construction contract”) (including the modified contents).

On February 10, 2012, the Plaintiff concluded a contract with the Defendant for additional construction works (emergency construction works) for sewage pipes in the instant project area for KRW 77,600,000 (hereinafter “the first additional construction contract for sewage pipes”).

On December 12, 2012, the Plaintiff entered into a contract under which the Plaintiff would receive a contract for an urgent construction work amounting to KRW 9,000,000 for the construction cost (hereinafter “the second additional construction contract for sewage pipes”).

Each of the instant cases.