Due to changes in the ratio of payment instruments in the structure of payments, payment market regulators, financial institutions, and real sector companies are faced with the question of what shape the payment system will take on in the future. Taking into account the possibility of performing all traditional (classical) functions of money with electronic money, as well as its great importance for users and society, we consider it appropriate to determine the directions and nature of expansion of the composition of the money turnover by including electronic money.

In our opinion, the issue of introducing e-money into the money turnover can be solved using a substitutional and additive approach.

Subconstitutionally, e-money acts as a substitute for traditional money, primarily cash, and is disclosed in terms of historical development of the category of money and its forms. According to the evolutionary concept of money came from the world of goods, i.e., the commodity is nominated by the commodity world for the role of universal equivalent in the process of long-term development of commodity exchange [36].

Thus, money in its development was initially in the form of real money, whose nominal value coincided with the real value. As a result of the growth of demand for money in the conditions of limited resources in circulation were issued inferior money, the nominal value of which exceeded the cost of resources spent on their manufacture. Later on, further expansion of commodity production, growth of exchange operations, and high costs of real money production led to the displacement of the latter by cost marks, in particular by paper and credit money.

In essence, paper money was a representative of real money; its objective possibility of functioning is conditioned by the function of money as a means of circulation, when money reveals its essence, acting as a universal intermediary in exchange processes. The complication of commodity-money relations, characterized by the emergence of a gap in space and time of exchange processes, has led to the emergence of credit money. The economic importance of credit money is to make the money turnover more flexible, able to reflect the need for money in the turnover of goods. Credit money is even more based on trust in its issuer.

Further development of commodity relations, rapid informatization of the society, active integration of information technologies and finance, and technological progress have formed the so-called information economy, which is characterized by the growth of economic value of information. One of the characteristics of the information economy is the dematerialization of reality and, respectively, the dematerialization of the money [37].

These circumstances led to the appearance of electronic money.

The idea behind this approach is that e-money is a formal substitute for cash in its form, as only cash currently has a physical form. According to the experts of the working group on the problems of the European payment system, the main purpose of electronic money is to promote alternative means of circulation in relation to banknotes and coins [38]. Their prospect is to reduce cash payments, first of all, to make small payments. A similar view is held by O. Issing in «New Payment Technologies: A Challenge to Monetary Policy», where he calls e-money private money, which competes with central bank money as a means of exchange  [39].

It should be emphasized that, from the perspective of a substitutional approach, the introduction of e-money into the money turnover is based on a historical and continuous process of money dematerialization. Electronic money is a natural stage of development of forms of money, the climaxes in the process of reducing the material content of the money. Electronic money is the result of the final stage of the process of dematerialization of the means of circulation.

Electronic money, performing all the classic functions of money, can become not only a formal substitute for cash, but also a functional substitute for both cash and non-cash money.

However, the complete abandonment of cash at this stage is almost impossible due to the following assumptions:

- in any case, the consumer strives to get the usual and convenient (tangible) payment instrument for him/her  [40];

- underdeveloped payment infrastructure;

- the cost of developing payment infrastructure on a geographical scale in large economies may be prohibitively high;

- high dependence of the ability to make payments on the reliability of the technical component of the payment infrastructure, as well as high risks of technical failures;

- low level of financial literacy of the population.

In addition, as noted above, it should be noted that e-money cannot be a full-fledged substitute for cash and non-cash money, as they have significant differences.

In this regard, it is advisable to consider an additive approach in which electronic money serves as an addition to the current cash and non-cash money. For this purpose, it is necessary to refer to the definition of money proposed by K. Menger. In his opinion, money is the money that has arisen under the influence of practices and habits of good that have the greatest marketing power in terms of time and place, is accepted in exchange by everyone and can therefore be exchanged for any other product. L. Mizes in his work «Human Activity», developing the position of K. Menger, also emphasized the main purpose of money to be a means of circulation. F. Hayek, talking about the essence of money, argued that there is a continuum in which objects with different degrees of liquidity and with different (varying independently of each other) values gradually pass into each other insofar as they function as money  [41].

 In other words, there are a number of objects with different liquidity. That is, what we call «money» is «the most liquid asset», which should perform only one function – to serve as a universally accepted means of exchange. Thus, according to the positions of K. Menger, L. Mises and F. Hayek, money is a good that has arisen under the influence of practice and habit in the form of the most liquid asset with no other consumer value as a widely accepted means of exchange  [42].

E-money is a special object, which appeared in the current conditions and has the greatest liquidity in these conditions. The most important purpose of electronic money is to carry out payment transactions on the Internet for the purchase of information, software products, access to certain resources. Thus, in these conditions, electronic money is the most liquid means of payment.

A fundamental difference between an additive and a substitutional approach is that e- money is presented as a new form of money, but not as a substitute for the traditional money that currently functions, but as a complement to it.

Thus, by looking at two scenarios of e-money development, where e-money substitutes mostly cash and partially non-cash, or where e-money supplements both cash and non-cash money mainly in the Internet trade sector, it is possible to determine the scope of e-money usage. In our opinion, e-money will be the most widespread in the following areas.

Firstly, the micro-payments sector, including the payments made on a regular or permanent basis (payments in transport, public catering organizations, as well as in cultural and mass organizations, parking fees, payments for communication and housing and communal services, etc.). In this case, e-money will function within the framework of a substitutionary approach, replacing traditional payment instruments because cash in this area may be less convenient because it has limited separability, which necessitates the provision of so-called surrender when paying with large banknotes or coins of greater denomination. This complicates and slows down the process of making a payment transaction in cash. The use of non-cash money for micro-payments appears to be unjustified due to more complex processing and, as a consequence, higher payment fees.

Taking into account the desire of the Ministry of Finance of the Republic of Kazakhstan to organize measures to reduce the use of cash in settlements43, the expansion of the use of electronic money in the sector of micro-payments and payments made on a regular basis, instead of cash will be a natural process.

A control value for electronic money is quite important. Cash is intended to serve individuals, but is virtually uncontrollable by the government. Therefore, cash is often the only way to service the monetary relationship in the informal economy. E-money to replace cash is more open, even though in most countries it is possible to make e-money payments with or without customer identification. Therefore, it is quite obvious that the turnover of electronic money is partially controlled by the state, and its development contributes to the expansion of state-controlled money turnover.

It should be noted that the use of electronic money, according to some researchers, allows the state to obtain significant savings associated with reducing the cost of circulation and cash withdrawal [44]. Indeed, the cost of processing cash is quite high and continues to grow. For example, the US Federal Reserve's expenditures on cash operations, which were in 2015, were as follows In 2016, the Company's net income increased to USD 398 million, up to USD 419 million. The costs of producing new banknotes are also high enough to replace those that have been withdrawn from circulation or to issue additional banknotes. The cost of producing new and replacing old cash is on average about half a billion US dollars per year. Today [45], statistics in Kazakhstan show that cash payments dominate: their share is about 90 % of the total volume of retail payments. Given that in Kazakhstan, according to National Bank of Kazakhstan calculations, cash handling costs are also quite large and make up about 1.1 percent of GDP, or 427 billion tenges [46], then electronic money, replacing cash, contributes to significant savings of financial resources.

In addition, Malaysian scientists believe that abandoning paper money will improve the environmental situation. As calculations show, if e-money replaces about 20 % of cash from paper, it will save about 1.8 million trees or [46] thousand tons of paper [47], Thus, e-money is of environmental importance. Second, the e-commerce sector, which is currently characterized by rapid development. According to experts, 1.6 million people in Kazakhstan made online purchases in 2018 [48]. In this sector, e-money will be manifested in line with an additive approach to expanding the composition of the money turnover, complementing traditional means of circulation and payment, serving the rapidly growing sector of e-commerce.

When operating in the e-money industry, e-commerce is of great integrative importance when it enables the flow of resources from the monetary sector to the real sector and vice versa [49]. According to D. B. Babayev, Formation of a common economic space within the framework of the «new economy» has four dimensions: the non-financial real sector, the financial real sector, the financial sector of the virtual economy, and the non-financial sector of the virtual economy. Electronic money, firstly, connects both sectors of the virtual economy by  analogy with the commodity and money circulation in the real economy, and, secondly, connect the virtual and real economy.

The user of electronic money, paying for purchases in the information and telecommunication network, may exercise his right to confidentiality of the transaction. Confidentiality cannot be maintained when paying with non-cash funds. Thus, it can be argued that e-money is a disguise for its users [50]. However, a disguise value that preserves confidentiality does not conflict with the electronic money benchmark mentioned above, as electronic money is then intended to replace uncontrolled cash flow in the first place. The disguise value of electronic money contributes to increased security rather than reduced control over transactions.

E-money is also indicative. First, the response of e-money to changes in the economic environment should be assessed as quite high, manifested in the possibility of rapid substitution of payments made within traditional payment systems with payments made within the framework of e-money systems. Secondly, e-money is an indicator of the level of development of monetary relations in the country. Thus, the monetary system in which e-money functions will be considered more developed than the one in which e-money does not function, is not recognized and has no legal grounds for functioning. Taking into account that money is a natural stage in the development of monetary relations in society, it is possible to judge the quality of these monetary relations, as well as the related non-monetary relations. In other words, the availability of electronic money in the money turnover will be an indicator of the development of these relations. The monetary system with functioning electronic money is more qualitatively advanced due to the fact that electronic money is a more convenient, efficient and less risky way of payment for use in new  markets and spheres of activity, such as the Internet, services provided by mobile operators, where payment by other means of circulation and payment is impossible, difficult or unreasonably expensive.

In this regard, we can talk about the incentive value of electronic money, which allows its owner to make payments and purchases in a completely new environment and new relationships in which there are no other opportunities for transactions. In addition, electronic money allows you to make payments in remote access mode.

The analysis carried out on the basis of various economic literature on the problems of theoretical identification allows us to draw a conclusion that electronic money is a very popular and very common research topic. However, in most cases, it is limited to examining certain aspects of electronic money functioning. It is precisely because of this that the necessity of fundamental research of economic-theoretical and applied nature is emphasized, forming a holistic vision of the problem of identification of electronic money and payment systems on their basis, the specifics of their functioning and development. In this regard, it is proposed to pay attention to the expediency of comprehensive development of this problem, which reveals the specific nature, functions, areas of the most optimal and effective functioning, as well as the importance of electronic money for users and the state.

In the course of the analysis of literature sources, all the many different positions and points of view on electronic money issues are combined into several key approaches. The usefulness and value of the method we use lies in providing a holistic view of how the many research aspects of electronic money and payment systems are reconciled in disclosing the functioning of electronic money and payment systems based on them.

We emphasize the role of the formal approach as the primary one in understanding the objective need for the emergence and essence of electronic money. Nevertheless, we justify the failure to fully disclose the essence of electronic money through the idea of this approach. Further we actualize the idea of identification of electronic money and payment instruments (methods and forms of settlements), where the key characteristic is the functional aspect (in terms of the function of the means of circulation and means of payment) of the object of research, and justify the idea of insolvency of recognition of electronic money as a monetary surrogate. Within the framework of the emission approach, the peculiarity of the issue of electronic money is disclosed. It is noted that this characteristic is the most essential of all necessary attributes of electronic money. Separately, the infrastructure approach was considered, which discloses the peculiarities of electronic money through the prism of the infrastructure used in the process of its functioning.

The individual approaches considered are not, in our opinion, complete and complete. Nevertheless, all the key points adopted by the approach are important to understanding. In this regard, there was an objective need to consider electronic money in a comprehensive manner. Definitions fixed at the legislative level and proposed by various financial and credit institutions were considered as complex interpretations of electronic money. The definition of electronic money (electronic money), enshrined in the Federal Law of 27.06.2011 № 161-FZ «On the national payment system» identifies them with one of the forms of cashless settlements. However, in our opinion, this fact imposes unnecessary restrictions and does not contribute to the development of new payment instruments, including those that would be used exclusively in the field of electronic money. However, the Law defined the legal status of electronic money as a legal tender. In concluding our review of key approaches, we conclude that the definition of e-money should contain only those attributes and characteristics that are purely intrinsic in nature. Thus, e-money is a dematerialized unit of purchasing power. Issued on a prepaid basis, accepted by persons other than the issuer, and the settlement of which does not require the exclusive and mandatory use of bank payment instruments.

In this chapter we have considered the functions of money and the possibility of its execution by electronic money, taking into account the previously identified features. As a result of the study it was found that electronic money performs all the functions that are inherent to traditional money. Nevertheless, it is the means of exchange that is the main function, which is the most popular and indicative. Other functions are secondary to the function of the means of circulation due to some unresolved organizational issues, as well as low level of public confidence in electronic money and security of payments with its use.

We also argue the approaches to expanding the composition of the money turnover by including electronic money. Within the framework of the substitutional approach, we emphasize the historical process of dematerialization of the means of circulation, which is accompanied by a gradual rejection of cash as an extremely expensive form of means of circulation. On the other hand, within the framework of the additive approach we consider the idea that the shift of economic relations into the sphere of information and telecommunication networks has also generated an objective need to create a convenient means of circulation in the conditions of new relations.

Considering the additive and substitutional scenarios of e-money development, we defined the spheres of e-money usage:

- first, the micro-payment sector, where e-money functions within the framework of the substitutionary approach;

- second, the e-commerce sector, where e-denas are manifested according to the additive approach.