The income over feed costs (IOFC) is an increasingly used tool for measuring efficiency in dairy cattle operations. One of the main advantages of the indicator is that it does not take into account fixed costs and subsidies. The indicator therefore assesses the relationship between milk sales revenue and feed costs. Based on data obtained every year from 62 to 114 dairy farms located in the Czech Republic in the period from 2012 and 2018, the average IOFC was 96 CZK per cow and day, with the inter-year variation ranging between 68 and 119 CZK. Fluctuations between the years under study were mainly due to the volatility of milk purchase prices, which affected daily incomes and thus the IOFC. In addition to milk prices, the indicator was also influenced by milk yield and feed costs. Moreover, the IOFC differences were due to differing production area characteristics and the breed used.