1) Language of business letters; 2) Language of legal documents; 3) Language of diplomacy; 4) Language of military documents; The aim: 1. to reach agreement between two contracting parties; 2. to state the conditions binding two parties in an understanding. Each of substyles of official documents makes use of special terms. Legal documents: military documents, diplomatic documents. The documents use set expressions inherited from early Victorian period. This vocabulary is conservative. Legal documents contain a large proportion of formal and archaic words used in their dictionary meaning. In diplomatic and legal documents many words have Latin and French origin. There are a lot of abbreviations and conventional symbols. The most noticeable feature of grammar is the compositional pattern. Every document has its own stereotyped form. The form itself is informative and tells you with what kind of letter we deal with. Business letters contain: heading, addressing, salutation, the opening, the body, the closing, complimentary clause, the signature. Syntactical features of business letters are - the predominance of extended simple and complex sentences, wide use of participial constructions, homogeneous members. Morphological peculiarities are passive constructions, they make the letters impersonal. There is a tendency to avoid pronoun reference. Its typical feature is to frame equally important factors and to divide them by members in order to avoid ambiguity of the wrong interpretation.