Abstract: The subject of the study is the regularities of the distribution of merged and hyphenated spellings of complex nouns in modern rules. Special attention is paid to identifying the main criteria for the design of the words of the studied group in the "Rules of Russian spelling and punctuation" of 1956, which still have the status of a set of spelling norms of the state language. Since the current rules are outdated, the work also considers the prescriptions of updated, but not having an official status, academic rulebooks: the complete academic handbook of 2006 and the newest electronic resource of OROSS "Spelling commentary of the Russian Dictionary" by E. V. Beshenkova, O. E. Ivanova, E. V. Tenkova. The novelty of the study lies in the fact that for the first time it analyzes the modern rules of spelling of complex nouns and the criteria underlying them. The established inconsistency of codification of these norms originates in the "Rules of Russian Spelling and Punctuation" of 1956 and is further developed in modern reference and educational literature, in particular in the complete academic handbook of 2006. As a result, it is concluded that it is necessary to include in the basic set of spelling rules a section containing the basic rules for distinguishing between merged and hyphenated spellings, set out briefly, simply and clearly.