The paper puts forward the hypothesis that money is a universal equivalent of stock of negentropy in the economy. The relevance of the research topic is underscored by the indispensable role of money in modern society. The paper generalizes the existing theoretical concepts of money, shows the way they solve the questions of whether money has intrinsic value, and what is the source of trust in money. We introduce the concepts of negentropy, source of negentropy, stock of negentropy and universal impersonal trust as a methodological basis of the negentropic approach to the substantiation of the essence of money in the economy. The importance of universal impersonal trust for ensuring the universality of money as an equivalent of stock of negentropy is shown. The essence of money as a universal equivalent of stock of negentropy is revealed. The laws of monetary circulation are explained from the point of view of the negentropic approach. We give an explanation of the functions of money in terms of the negentropic approach. Similarities and differences of the author’s hypothesis with already existing alternative theories of money essence are shown. The advantages and disadvantages of the negentropic approach to the substantiation of the essence of money are discussed, possible areas of practical application of the hypothesis are outlined. The conclusion gives recommendations and prospects for using the hypothesis of the essence of money as a universal equivalent of the stock of negentropy in the economy.