A. Comprehensively taking account of the overall purport of the statements and arguments by Gap evidence Nos. 1 through 3 as to the cause of the claim, the plaintiff and the defendant may recognize the fact that the plaintiff supplied interior building materials to the defendant, and the defendant concludes an agreement to supply goods to the plaintiff on the last day of the month in which a tax invoice is issued by the plaintiff and to pay the price to the plaintiff on the last day of the month in which the issue date belongs, and that the plaintiff supplied indoor building materials worth KRW 33,49,070 in total at the construction site located in the Daegu Suwon-gu Yellow-dong 890-5, Nov. 17, 2014 during the period from October 10 to November 17, 2014, the plaintiff issued an electronic tax invoice (hereinafter referred to as "electronic tax invoice of this case") and delivered them to the defendant on December 10, 2014.

Therefore, barring any special circumstance, the Defendant is obligated to pay to the Plaintiff KRW 33,49,070 of the price of supplied interior building materials and the Plaintiff at the rate of 6% per annum as stipulated in the Commercial Act from January 1, 2015 to June 3, 2015, which is the date following the end of the month when the electronic tax invoice was issued to the Plaintiff, the original copy of the payment order in this case, and at the rate of 20% per annum as stipulated in the main sentence of Article 3(1) of the former Act on Special Cases Concerning Expedition, etc. of Legal Proceedings until September 30, 2015 (wholly amended by Presidential Decree No. 26553, Sept. 25, 2015); and the damages for delay calculated at the rate of 15% per annum as stipulated in Article 3(1) of the same Act and the main sentence of Article 3(1) of the former Act on Special Cases Concerning Expedition, etc. of Legal Proceedings (wholly amended by Presidential Decree No. 26535, Sept. 25, 25, 2015, 2015).

The Plaintiff sought payment of damages for delay from December 10, 2014, which is the day when the tax invoice was issued to the Defendant, but the Plaintiff issued the instant electronic tax invoice.