The postulate embedded in the civil legislation – good faith in actions – as a parameter that models the behavior of participants in civil turnover stimulates the development of behavior in which none of the participants in the obligation can take advantage of deliberately maneuvering in a situation of regulatory gaps. Representing an evaluation category without clear criteria, the content of the principle of good faith is formed under the influence of legal doctrine and law enforcement practice. In the conditions of a legal gap in regulating the time of an R&D contract performance and the acceptance of the result of the work performed, the customer’s bad faith, expressed in delaying the acceptance of the work, or the refusal of the results on far-fetched pretexts, is not uncommon. The purpose of the research is to study the legislative and law enforcement aspects of the customer’s unfair behavior in R&D contracts at the time of their execution, as well as to develop proposals for improving civil legislation. Methods. The methodological framework for the research is a set of methods of scientific cognition, among which the main ones are analysis, synthesis, generalization, and comparative jurisprudence. Results. In the activities of companies related to the performance of work under R&D contracts, the problem of the customer’s bad faith at the time of contract execution and the acceptance of the work performed belongs to the category of urgent, as numerous judicial practices abound. Proactive, preventive measures on the part of the contractor, expressed in a more detailed elaboration of the terms of the contract, do not have a positive effect and are not a guarantee of the contractor’s security. The author analyzes the current judicial practice on economic disputes for the possibility of applying the rules on the analogy of the law in the conditions of the gap in the civil legislation on the unilateral signing of the act (Chapter 37 of the Civil Code of the Russian Federation). Currently, there are two polar approaches in the legal realization sphere: 1) the rule on signing an unilateral act as a highly specialized one can be applied exclusively in the form of a construction contract (negative approach); 2) following the principles of fairness and reasonableness enables the contractor under an R&D contract to apply the provisions of Article 753 of the Civil Code of the Russian Federation to protect his interests (positive approach). Conclusions. The existing legislative gap in the formation of diametrically opposite ways of resolving judicial conflicts and the duality of judicial practice should be resolved exclusively at the legislative level by amending Paragraph 1 of Chapter 37 of the Civil Code of the Russian Federation. In particular, Paragraph 2 of Article 720 of the Civil Code of the Russian Federation should be supplemented with the following content: “The submission of the working results by the contractor and its acceptance by the customer are executed by an act signed by both parties. If one of the parties refuses to sign the act, a note about it is made therein, and the act is signed by the other party.”