The model of a salary calculation system in Poland is introduced. Great complexity of the process of salary calculation caused by bureaucracy and many difficult law acts requires a special attention to application designers. In order to calculate salary for different enterprises in Poland, a special model must be implemented. The chapter is divided into four sections in which we characterize the specificity of Polish salary calculation process and propose the model that has been successfully implemented in a commercial system. The model comprises of two components: data structures and methods.