The article is devoted to a critical analysis of the concept created in the jurisprudence of considering a partner of a two-person limited liability company as an "illusory partner" and, as a consequence, attributing to the second partner the status of an "almost sole" partner for social insurance purposes. Such a qualification means that the "almost sole" partner cannot be employed in that company on the basis of an employment contract, and therefore such a person is not subject to social insurance on that account, but should be insured as a partner of a one-person company (i.e. a person running a non-agricultural activity). The authors present doubts concerning this concept both on the basis of national legislation and the Convention for the Protection of Human Rights and Fundamental Freedoms.