The subject of the article is the analysis of court decisions referring to the concept of "cooperating person" expressed in art. 8 sec. 11 of the Act of 13 October 1998 on the social insurance system. Elements of the definition of "cooperating person" contain unspecified phrases such as: "remaining in a common household" and "cooperation in conducting business". This requires the courts to make findings regarding the factual circumstances of the case being considered and then to make subsumption, which leads either to the application of art. 8 sec. 1, 2, 11 in connection with art. 6 sec. 1 item 4 or 5 of the Act on the social insurance system, and thus to the coverage of individual persons with mandatory retirement and disability insurance or to the refusal to apply the above-mentioned norms. This work is a review article, the main purpose of which is to determine what elements of the factual situation are taken into account during the explanatory proceedings conducted by courts adjudicating in cases, the subject of which is to decide whether a given person meets the requirements included in the definition of a "cooperating person" in accordance with art. 8 sec. 11 of the Act on the Social Insurance System, and the evolution of the definition of a cooperating person was discussed as part of the introductory issues.