ENThe article presents the career mechanisms of the Lithuanian treasury scribe Samuel Hieronim Kociełł (d. 1685). He amassed a considerable fortune by providing financial services to the most important Lithuanian magnate families (mainly the Radziwiłłs and the Sapiehas). He was also successful in political activity, in which he joined the Pacs’ party, becoming its leading activist at the sejmik of Oszmiany. The legacy he left behind laid a solid foundation for the socioeconomic advancement of his family. Keywords: treasury officials, treasury office, political career, social advancement, patron-client ties. [From the publication]