1. The Defendant paid KRW 547,985,00 to the Plaintiff KRW 6% per annum from August 8, 2018 to July 9, 2020.

1. Basic facts

A. The Plaintiff is a company aimed at the electrical construction business of buildings and the solar power generation business, and the Defendant is a company aimed at solar power generation business.

B. On January 2012, the Plaintiff’s implementation and completion of a new telecommunications and fire fighting equipment installation project related to D’s new construction in the Defendant’s located in the Defendant, Dak-gun, Gyeongnam-gun (hereinafter “D electrical construction”).

C. On April 28, 2017, the Defendant: (a) specified installation works for the supply of raw and secondary materials and structures (hereinafter referred to as “construction works for solar power plants”) to newly construct solar power plants (two factories) on the ground, Gyeongnam-gun, Gyeongnam-si; (b) based on the contract amounting to KRW 690,00,000 (excluding value-added tax) and June 30, 2017 (hereinafter referred to as “instant solar power plant contract”); and (c) supplied secondary materials and structures (hereinafter referred to as “construction works for solar power plants”) to newly construct solar power plants (three factories) on the ground, Gyeongnam-gun, Gyeongnam-gun, and determined the contract amount to KRW 690,00,00 (excluding value-added tax) and the contract amount to complete the completion of the construction works for solar power plants (hereinafter referred to as “solar power plants”) on June 30, 2017.

Each solar power plant contract of this case is commonly defined as “10,000,000 won in the contract amount after the conclusion of the contract and intermediate payment of KRW 150,00,000 in the intermediate payment after the conclusion of the contract, and the intermediate payment of KRW 150,000 in the form of the structure and the intermediate payment of KRW 150,000 in the form of a structure after the completion of the pre-use inspection.”

On August 2, 2017, the Plaintiff and the Defendant respectively changed the contract amount of the construction of solar power plants to KRW 722,953,00 (including value-added tax) and KRW 725,032,00 (including value-added tax) for the construction of solar power plants, and KRW 725,032,00 (including value-added tax) for the completion of each construction work on August 30, 2017.

The Plaintiff completed the construction of solar power plants of heading 2 and 3, and the Defendant obtained approval for use under the Building Act for each solar power plant on April 7, 2017.

E. The defendant