Nowadays social security of population is dynamically expanding its subject of legal regulation as well as changing the methods of managing the social and legal relationships.

 Pension insurance being the part of social insurance is particular because of the risk which concerns the retirement age. This aspect and the difficulties associated with the pension risk insurance have caused the gradual rejection of the principles of insurance in many countries.

 The insurance pension risk is characterized by the necessity of its previous recording and measurement to determine the differentiated contribution rates. Since January 1, 2011 a single social contribution has been introduced in Ukraine and it serves as an analogy of the four previous payments paid by taxpayers as a fee for the compulsory state social and pension insurance.

 The mechanism of the pension insurance having been complicated makes it necessary to research its essence as a special social phenomenon. Market economy requirements indicate the need of clear understanding of the economic and social factors’ interaction, as the search for the stable funding sources and formation of the valid system of financial security is the issue of the high importance for any state.

 This is especially true for the pension law where there is a clear tendency of public and private principles’ convergence on the different levels of the pension system. Thus, to explore the legal nature and history of this question is the main purpose of this article.