According to the wording of Article 968 § 1 of the Code of Civil Procedure, the purchaser may set off his own claim or part thereof against the price if it is covered by the purchase price. The subject may cause problems in its practical application. It is not clear from the real estate foreclosure regulations who the purchaser is who is entitled to credit the claim against the purchase price. In addition, the legislator has not specified how the claim covered by the purchase price is to be understood. The manner and form of crediting a claim against this price, including a claim secured by a mortgage, is also not concretized. Also disputed in the doctrine is the question of the legal consequences of the buyer of real estate paying too low a purchase price following the improper crediting of a claim against this price. The purpose of the article will be an attempt to resolve the mentioned research problems. An attempt will also be made to assess whether the current wording of Article 968 § 1 of the Code of Civil Procedure sufficiently defines the rules for an auction purchaser to take advantage of the institution in question.