The subject of the article is the issue of verification by Social Insurance Institution (ZUS) of conducting business activity as a title of social insurance and the contribution calculation basis of social insurance declared by the insured (entrepreneur). In this area there are no controversies as to the legitimacy of questioning the business activity as a social insurance title by the pension authorities. The author expresses, however, a more far-reaching view and, approving the Supreme Court's position presented in the judgments in cases I UK 208/17, II UK 301/17 and II UK 302/17, he believes that ZUS is also competent to verify the declared contribution calculation basis on this account. Therefore, the main purpose of the article is to present a wide range of arguments in support of the defense of the above thesis in confrontation with the older case law of the Supreme Court and the most recent literature in this area, in which such actions of ZUS are considered inadmissible.