A. The Plaintiffs, who entered into a contract for construction works, agreed to newly construct the instant housing on the said ground after purchasing 315.6m2 in Seongbuk-gu, Sungnam-si.

On October 19, 2009, the plaintiffs prepared a design application stating the requirements of the plaintiffs through E, who had been in charge of business as the employees of the defendant's external business.

At the time, the Plaintiffs were eligible to apply heavy tax rates because the total floor area of the building exceeds 331 square meters under the Local Tax Act, and thus, they were required to newly construct the housing area of this case below 100 square meters (330.57 square meters). The Plaintiffs stated the application for design as “PLN OTAL 100 square meters.”

A contracting officer F and design officer G, who are employees of the Plaintiffs, E and the Defendant, entered into a contract for construction works on November 30, 2009, after conducting an interview based on the above design application and paying an estimate.

(hereinafter “instant contract”). According to the said contract, the total area of the instant housing was calculated as 322.81 square meters (14.8 square meters on an underground 1st floor, 43.25 square meters, 144.8 square meters, 134.76 square meters) with the exception of 13.24 square meters on a rooftop, which is a part not included in the total floor area under the Building Act.

B. The instant housing was finally constructed with 42.94 square meters on the underground floor, 144.58 square meters on the 1st floor, 2nd floor, 134.76 square meters on the 13.25 square meters on the 2nd floor, and 13.25 square meters on the 10th floor on the 2010, and the Plaintiffs reported and paid acquisition tax calculated by applying general tax rates on the acquisition of the instant housing around August 30, 2010, KRW 11,818,180 and special rural development tax on the 1,181,810.

Article 112(2) of the former Local Tax Act (wholly amended by Act No. 10221, Mar. 31, 2010) on the ground that the portion of the instant rooftop is included in the total floor area of the instant house to the Plaintiffs around September 27, 201, and that the total floor area exceeds 335.53 square meters, and the value of the building exceeds 90 million won, and constitutes a de facto house (wholly amended by Act No. 10221, Mar. 31, 2010).