The study includes an analysis and evaluation of the time series of expenses of the research subject. The distribution of the analyzed data was examined with the use of graphs, such as: a histogram, normality and the Shapiro-Wilk test. The existence of outliers and extreme values was then searched for with a box plot. Chernoff Faces were then used to detect the monthly seasonality in the time series of the expenses under consideration. The regularities in the form of trend and seasonality detected during the data analyzes were confirmed by the binary model of multiple regression. The study includes forecasting of the time series of expenses with the use of the Klein model. The last stage of the research was the analysis and evaluation of the remainder of forecasts. The forecast of expenses for 2021 is an amount of PLN 575 248 346. In 2022, it increased to PLN 676 989 270.