The formulation of contractual penalties in public procurement still encounters numerous qualification-related difficulties, related in particular to the selection of the title of the penalty adequate to the breach of contractual obligations and the optimization of its amount. Their rationalization is justified not only by the protection of public interests and the public law obligation to pursue claims, but also by the common idea of contractual justice. Recently, there have been increasing difficulties in interpreting the new provisions against abusive clauses, introduced unjustifiably to the disadvantage of contractors to adhesively designed public procurement contracts, subject to appeal review before the National Chamber of Appeals. Interpretation uncertainties regarding the permissible accumulation of penalties under various titles and the mandatory determination of the maximum limit of all penalties are also significant. The purpose of this article is to explain these difficulties, combined with a proposal for a functional interpretation of the questionable provisions.

The admittance of substitute performance of a contracted service by a third party at the contractor's expense, as a type of fulfilment of the debtor's financial liability, especially in the event of falling into delays or the defective performance of a public contract, constitutes the reinforcement of the principle of real performing a contract, which is important from the point of view of the effective satisfaction of public needs. The alternative form of liability being the rescission of the contract by the contracting authority, while retaining the right to compensation or demanding the payment of a contractual penalty does not always sufficiently satisfy its interests. The authorization of the contracting authority to apply substitute performance can arise directly from the Act, although it only applies to rare, exceptional situations, or a court order. The significance of an authorization arising from a previous contractual provision has recently been increasing. However, this basis poses difficulties of qualification, primarily of a structural nature. The principle of the real performance of a contract can also be implemented by filing an action against an unreliable contractor for a performance in kind, although enforcement difficulties can be avoided by a court order authorizing substitute performance by a third party at the contractor's expense.