The article is devoted to both theoretical and practical aspects of the problem of the basis for assessment of social security contributions for a lump sum obtained by a member of the board of a limited liability company employed in this company under a contract of employment. For the proper presentation of the issue the author discusses the organizational relationship and employment relationship between the board member and the company, and then makes a synthetic summary of the features that distinguish these two legal relationships. These considerations conclude the analysis of four possible configurations that allow to determine the basis for the calculation of social security.