Abstract: This article discusses the features of letters of recommendation: types, structure and criteria for evaluating work certificates. The relevance of the work lies in the fact that letters of recommendation have been around for a long time and are an integral part of the business sphere in Germany. Given the lack of workbooks in Germany, providing a letter of recommendation for consideration by a potential employer is a prerequisite. This speech genre requires detailed attention and consideration from the point of view of linguistic and structural features. The object of research is the speech genre "recommendation letter". The subject of the study are structural and substantive features, types of letters of recommendation. The purpose of the work is to consider the types and features of letters of recommendation in the German language in a diachronic aspect. The scientific novelty of the research lies in the fact that for the first time the types and linguistic characteristics of the German-language recommendation letter are studied from the standpoint of diachrony. The research material was a German website containing archives of old letters of recommendation: Arbeitszeugnis-forum.de.In the course of the study, it was found out that the most preferable is a qualified letter of recommendation containing a detailed description of the employee and opening him a wider range of further career opportunities. Qualified recommendation letters in German have the following features: 1) a letter of recommendation must comply with the principles of truth and benevolence, therefore it must be written positively; 2) a qualified letter contains information about the work performed, various qualities and achievements of the employee, about his behavior among colleagues and clients, as well as thanks and wishes for the future. The analysis of letters of recommendation showed that until 1900, there were mainly simple working certificates in use in Germany. The letter of recommendation did not have a clear structure. The qualified certificate has received great relevance and has been supplemented with characteristics, approximately, since the 1940s.