The financial stability at the macro level mainly refers to the state of equilibrium in the system operation, where the financial system efficiently performs its key economic functions, such as resource allocation, risk transfer, and making payments, and can do so in the event of shocks, stressful situations, and periods of profound structural changes [17]. The financial sustainability is primarily considered as a property of the financial system to return to equilibrium after cessation of the impact of certain negative factors [18]. According to V.N. Alferov, the financial stability of the company is the state and distribution of its financial resources, which ensure the company development, its solvency and investment attractiveness in terms of tolerable risk [19].
At the same time, T. Kovaleva equates these two concepts and explores them much broader, not reducing only to the state of the financial system. In particular, T. Kovaleva believes that the financial sustainability reflects the property of the entire economic system rather than the financial system in the narrow sense, and should be understood as the state of its operation, when a) it is in a dynamic state of financial equilibrium; or b) its deviation from equilibrium lies within the prescribed limits in case of exogenous or endogenous shocks, and it is able to return to financial equilibrium mode [20].
FI is primarily associated with a specific situation where "the economy operation potentially deteriorates with price fluctuations of financial assets or the inability of financial institutions to meet their contractual obligations" [21], when "prices of some key financial assets deviate sharply from their fundamentals, and the operation of credit markets is thrilled, due to which the aggregate expenditures deviate significantly from the normal level" [22]. As a result, the functioning of the key elements of the financial system is disrupted, and the latter is unable to withstand shocks and prevent their destructive impact on the real economy [23].