Over the past seven years, significant changes have occurred in both the development paradigms and the practical use of software systems of varying complexity. These changes are largely driven by the rapid adoption of online artificial intelligence technologies based on large-scale language models. Such models are currently actively used in software development tasks, including source code generation and test plan creation, thereby integrating across various stages of the software development lifecycle. This article examines a classic research object—namely, the process of developing a system requirements specification—and proposes an approach to its formal verification using the ChatGPT online service. First, a detailed mathematical formalization of the research object is presented, followed by a structured model for preparing system requirements in projects using ChatGPT at various stages of development. Next, the proposed approach is illustrated using a real IT project example, demonstrating the sequential stages of requirements preparation in a modern development environment. The article defines the main categories of system requirements and discusses their representation in project documentation. To support the analysis, relevant tabular data and UML diagrams are provided. Furthermore, the study describes a methodology for formal requirements verification through prompt-based interaction with the ChatGPT system. The scientific novelty of this work lies in the application of requirements verification by modeling the expected behavior of the future software system using ChatGPT. Future research directions include incorporating a fifth category of requirements – business rules – using ChatGPT, which will enable modeling the behavior of the software system in real business processes.