Business correspondence always serves communication with a clear purpose, deals with urgent and topical issues and is addressed to a specific communication partner. Partners, goals, conditions, methods and organization of communication in written communication form the structure of business discourse. The full and accurate application of these components in business correspondence allows for positive and effective communication. The article deals with the texts of business letters written in the Azerbaijani language, which is one of the main means of business communication. A business letter is a legally binding business document that serves to enter, store and transmit information. Writing business letters involves a certain reaction of the addressee, that is, within the communicative situation, one letter is followed by a series of thematic texts related to it - reply letters. Categories of business discourse are applied in the official sections of the business correspondence document and directly in the text itself. The analysis leads to the conclusion that the rational compatibility of standard elements and standardized lexical, morphological and syntactic language units and means at all levels of the language is reflected in all sections of the business letter in the Azerbaijani language. The article considers the characteristics of different categories of business discourse in the genre of business letter, reflecting this rational correspondence. The expediency of the analysis of the texts of business letters within the discursive approach is substantiated.