According to § 1914 odst. 1 ObčZ, it is stated that payment may be made to someone else for performing certain actions. § 2165 odst. 1 ObčZ and § 2100 odst. 1 ObčZ refer to the relationship between them. The diploma thesis aims to analyze the liability of the seller for defects in goods sold in a shop. Through historical analysis, the author shows that current literature is a result of the Czech mix of the obligation to report faults and the time limit for making a claim. The relationship between the different regulations is based on the principle of lex specialis derogat. § 1914 odst. 2 ObčZ specifies the effects of defective performance, which can cause the obligation to cease and result in a separate contractual relationship between the parties. There is a difference between partial performance in § 2004 odst. 2 ObčZ and normal performance in § 1914 odst. 2 ObčZ. Anyone who accepts a position in a chosen authority is obliged to carry it out with loyalty, knowledge, and diligence.