This academic article offers a model of the English-Ukrainian sub-corpus of texts of official and business documents of NATO, UN, and WTO (hereinafter referred to as the EUS) as a supplement to the Ukrainian National Corpus (hereinafter referred to as the UNC), where texts are presented as a hierarchical structure. In an effort to provide a more comprehensive view of NATO, UN, and WTO official and business documents, a mechanism of use of our model envisages determination of the exact position of a text in all UNC corporas, what essentially simplifies the practical process of search and automated translation of texts and special terminology in particular. In consequence, the author offers to increase the number of unique texts that will ensure the representativeness of the EUS in the Ukrainian National Corpus, and to divide the whole process of the EUS formation into elementary tasks that will increase the UNC efficiency. The practical value of the research lies in a possibility to use the EUS for texts parallel translation and terminological phrases separation on the basis of such texts. The methodological potential of our research is based on the works of well-known Ukrainian and foreign scholars (V. Bohorodytskyi, I. Baudouin de Courtenay, K. Brugman, W. Wundt, B. Delbruck, G. Paul, O. Potebnia, P. Fortunatov, W. Scherer, H. Steinthal, A. Schleicher et al.), who strengthened the scientific interest to the problem of translation and corpus of texts in particular. The object of the research is a model of the English-Ukrainian sub-corpus of texts of official and business documents of NATO, UN, and WTO. The purpose of the research is to prove that the model of the English-Ukrainian sub-corpus of official and business documents texts can become a full-fledged informational foundation for the formation of texts parallel corpus within the Ukrainian National Corpus. The methods of observation and experiment were applied to analyze empirical, review, conceptual analytical tools that specify the meaning of described objects and phenomena given their qualitative affiliation to the UNC. The study focuses on a number of tasks, in particular: - to determine a theoretical and linguistic basis of the concept “English-Ukrainian sub-corpus of texts of official and business documents of NATO, UN, and WTO”; - to determine the mechanism of updating of the English-Ukrainian sub-corpus of texts of official and business documents of NATO, UN, WTO within the UNC; - to find out the specifics of formation and filling-in of the EUS; - to substantiate the relevant methodology of examination of official and business texts of NATO, UN, and WTO in the English-Ukrainian sub-corpus of texts of official and business documents; - to single out and itemize the advantages of the English-Ukrainian sub-corpus of texts of official and business documents of NATO, UN, and WTO within the UNC. Analysis of the English-Ukrainian sub-corpus of texts of official and business documents of NATO, UN, and WTO as a construct of the parallel corpus of texts of the UNC was carried out in several stages. The first stage envisaged description and inventory. Theoretical works on the history of the Ukrainian National Corpus were reviewed and generalized, and the concept of “English-Ukrainian sub-corpus of texts of official and business documents of NATO, UN, and WTO” was determined. It was found out that the UNC is the object of research in such areas of linguistic studies as the applied and corpus linguistics that construe the corpus of texts as a translator’s tool. This encourages us to highlight the advantages and disadvantages of the UNC and justify the expediency of our proposal to develop the English-Ukrainian sub-corpus of texts of official and business documents of NATO, UN, and WTO. Definition of the UNC as a national corpus of texts that contains only Ukrainian texts and does not envisage a parallel translation evidenced the need to create a proposal of a parallel corpus of texts with an updated English-language database. The selection of lexical items with the official and business semantics is based on documents of international organizations, such as NATO, UN, and WTO. At the same stage, we determine the purpose of the research, in particular, the formation of the English-Ukrainian sub-corpus of texts of official and business documents, which envisages a parallel translation of NATO, UN, WTO texts. This sequence of procedures allowed us to carry out consideration and interpretation of existing theoretical provisions and inventory of factual research materials. Theoretical and corpus analysis methods were used in the research. The second stage envisaged analysis and differentiation. Special aspects of filling-up of the EUS with official and business texts of NATO, UN, and WTO were characterized. Theoretical analysis of the EUS was carried out in order to establish a clear hierarchy of the UNC structure. The main types of participants of the EUS formation (students, teaching staff) were differentiated and the behavioral model of every participant in the process was developed. The specifics of presentation of the English-Ukrainian sub-corpus of texts of official and business documents of NATO, UN, and WTO in the UNC was established. This final stage, where methods of observation and experiment were used, evidenced determination of an exact place of a text in the EUS (belonging to a certain category of homogeneous texts) that becomes a crucial factor in choosing a translation option. Numerous terminological phrases and expressions in the analyzed official and business documents of UN, NATO, WTO, which act as identifiers in the EUS, were systematized. An increase in the number of unique texts (official and business texts) was noted, which ensures the representativeness of not only the English-Ukrainian sub-corpus of official and business documents texts, but of the UNC in general. The final stage of the research confirmed the expediency of the division of the whole process of sub-corpus formation into elementary tasks. We generalized the statement that the EUS is a dynamic, context-dependent sub-corpus (only official and business texts of international organizations, such as NATO, UN, WTO) and an optimal algorithm designed to be easily downloaded and used. Conclusion. The analysis conducted in the present paper is meant to illustrate a new approach to forming a modern model of the sub-corpus of texts of official and business documents. The model of the English-Ukrainian sub-corpus of official and business documents texts of NATO, UN, and WTO provides for a clear division into categories of homogeneous texts and a quick search for special terminology of international organizations, such as NATO, UN, and WTO, in the EUS. In the context of the texts analyzed in the current paper numerous separated words and expressions-identifiers can help to carry out search and refer to a relevant text in the sub-corpus. Compilation of terminological nominations glossary, their functional and stylistic labeling and assimilation into the commonly used vocabulary of the EUS and later on in the UNC are currently at the stage of formation and approval. To this end, the current research manifests the concept of the EUS as a sub-corpus of the UNC that allows the prompt presentation of relevant texts of the official business style and coverage of the broadest range of interested readers.