The purpose of the study is to compare two methods of demonstrating compliance with the conditions for participation in the public procurement procedure and to determine whether the provisions of polish public procurement law adequately regulate the situation of contractors using any of them. Polish and EU public procurement law allows economic operators to rely on the capabilities of other entities or members of a group of economic operators in order to demonstrate compliance with the conditions for participation in the procedure. Combining a capabilities with other entities or with members of a group of economic operators serves various purposes. Nevertheless, the rules for subjective qualification should be analogous. In fact, they differ from each other in two important issues: the rules for correcting errors revealed during subjective qualification and the rules for liability for non-performance or improper performance of a public contract are different. The Public Procurement Act should be amended in these areas. Moreover, the amendment should also concern a provision regulating the subjective change of the contract – it should precisely regulate the admissibility of changes in the composition of the group of economic operators.

The purpose of the study is to analyze the status of the tenderer under the Public Procurement Law, in particular: determining the temporal limits of this status, the rights and obligations of the entity entitled to this status, and to examine the internal dynamics in the group of tenderers. In a public procurement procedure based on a tender model, three stages can be distinguished: pre-bid, bid and pre-contract. Article 7.30 of the Public Procurement Law enables the identification of four categories of economic operators, only two of which refer to participants in the procedure. The status of the candidate is linked to the pre-bid phase of the procedure, while the status of the tenderer is activated with the start of the bidding phase, and ends with the completion of the pre-contractual phase i.e. the award of the contract. The composition of the group of bidders as well as their rights and obligations are changed when the result of the procedure announced by the contracting authority becomes final. While at the bidding stage, tenderers have the right to actively act to maintain their offer in the proceedings or eliminate competitors' offers, at the pre-contractual stage, nonselected contractors can only wait for the reactivation of the bidding stage, which may happen if the tenderer whose offer has been selected refuses to conclude the contract.

The aim of the article is to discuss the consequences of the expiry of the validity period time of the offer submitted in the public procurement procedure and to evaluate the solution introduced to the Public Procurement Law of 2019 from the perspective of the Civil Code, which establishes the general legal regime for economic transactions. According to civil law, an offer that ceases to bind expires so acceptance of such an offer does not lead to a legal relationship (contractual or pre-contractual). The Public Procurement Law of 2004 did not regulate the effects of the expiry of the offer's validity period, which was the source of doctrinal disputes and discrepancies in jurisprudence. The judgment of the Court of Justice of the European Union in Case C-35/17 has dispelled these doubts only to some extent. The solution adopted in the Public Procurement Law of 2019 entitles the contractor to express a consent to the conclusion of the contract, which in the civil sense is a renewal of the offer. The model designed as a compromise between ensuring the effectiveness of tender procedures and the need to be consistent with the basic structures of civil law raises a number of doubts. It creates a non-tender phase of the public procurement procedure, which makes it difficult to describe the legal situation of the participants using traditional civil law terminology.