The author proves the necessity of publishing of the documents concerning functioning of inner custom offices in the first half of the 18th century. These documents are kept in different archives and unknown to Russian linguists. It is important that all the documents are dated and include the information concerning the locales where they were issued. Vocabulary of the sources can potentially broaden linguistic knowledge of the Russian language vocabulary of the 18th century. Quantity of preserved documents, scale of their geographic area, diversity of their types and kinds, and local origin of the writers do not let us underestimate their linguistic value.