The article analyzes antimonopoly and judicial practice of determining the amount of penalty and the procedure of charging it under the RF Law "On the Procurement Contract System." The author considers the manner in which the contractor entrenches conditions that stipulate liability in the contract analyzing and explaining approaches of antimonopoly authorities and courts. Particular attention is paid to the penalty retention from a bank guarantee and monetary funds. The article shows interrelation between the mechanisms of penalty, bank guarantee and monetary funds. The author examines the issues of interrelation between fines, penalties and grounds for imposing them, justifies the statement concerning unreasonably high amount of legal penalties imposed on suppliers, analyzes risks associated with excessive amount of penalties for both customers and suppliers. The article proposes to address the issue of penalties in terms of the need to balance private and public interests within the framework of the procurement contractual system.