The article studies the titles of documents of Western Russian origin that enriched the nomenclature of document genres in the era of Peter the Great's reforms. The administrative reforms of Peter the Great were reflected in the transformation of not only the system and principles of governing the country, but also the business language that accompanies governing activities. The business language of the Peter the Great era included new lexical and grammatical elements, changed the principles of document design and, among other things, was replenished with new document genres. In the scientific literature, new titles of documents are usually considered either as borrowings from European languages (including through Polish mediation) or as nominations created in the Russian business language based on Church Slavonic models. The analysis of some titles of documents presented in the article shows that such a view of their origin is simplified. The studied titles of documents were divided into two groups: those formed based on Slavic models (doneseniye, donosheniye, prosheniye) and those of European origin (artikul, dokument, instruktsiya, kvitantsiya, relyatsiya). As a result of comparison of historical dictionaries and extensive text data, including documents of pre-Petrine Rus, of Western Rus of the 15th–17th centuries, of Peter the Great era, as well as of Polish documents, it was concluded that these titles of documents were present in the documentary speech of Western Rus long before Peter the Great’s reforms, having entered it from the Polish language. Thus, the analysis of the titles of documents leads to the conclusion that Peter the Great’s reforms copied the administrative experience of not only Western Europe, but also of its closest neighbors – Western Rus, including the Western Russian business language. Apparently, the speech skills of the emperor’s associates, many of whom were of Western Russian origin, played a significant role in the penetration of Western Russianisms into the business language of the Peter the Great era.