A. On February 18, 2013, the Defendant entered into a subcontract (hereinafter “instant contract”) between the Plaintiff and the Plaintiff, under which the part of the panel construction among “B construction works” within the female national industrial complex (hereinafter “instant construction works”) was awarded a contract with ELD Construction Co., Ltd. (hereinafter “original Office”), and between the Plaintiff and the Plaintiff, the construction cost of the said construction works is KRW 560 million (excluding value-added tax).

The above construction cost was calculated by adding up the amount calculated by applying 89% of the contract unit price applied between the defendant and the original office after calculating the size, quantity, etc. by item concerning the instant construction project based on the design documents, etc. prepared by the original office.

On the other hand, Article 8 of the contract of this case states that ① there is no advance payment, ② progress payment shall be paid according to its contents and proportion within 30 days from the date of receipt by the original office, and ③ in the case of increase and decrease in the quantity and price adjustment due to a design modification, etc., it shall be paid after mutual agreement within 60 days from the date of receipt by the original office.”

B. During the construction process of the instant construction project, the work volume and contractual unit price adjustment was made due to the design change and price increase by the headquarters. The Plaintiff, accordingly, continued the construction project and completed around June 2013.

On June 11, 2013, the Plaintiff sent to the Defendant a document for settlement of accounts calculated as KRW 722,188,500 by reflecting the work quantity, etc. changed by e-mail to the end of the instant construction.

On July 22, 2013, C, the Defendant’s on-site director, sent to the Plaintiff a settlement document calculated as KRW 627,767,670 by e-mail.

C. On March 6, 2014, the Defendant settled the instant construction cost as KRW 704,876,593, and received all the balance of the construction cost settlement from the original office on April 10, 2014.

On the other hand, the plaintiff is now going against.