The purpose of this research was to compare nitrous oxide (N2O) emissions using the IPCC methods − first (Tier 1) and second level (Tier 2). Calculation on the second level was performed using a Global Nitrous Oxide Calculator (GNOC). The calculations showed that based on the Tier 1 methodology average N2O emissions for Poland were 3.51 kg N/ha, whereas for the GNOC calculator − 2.74 kg N/ha. The obtained results indicate that the use of GNOC calculator which takes into account agro-environmental conditions allow for accurate estimations of N2O emissions when drawing up reports in accordance with the commitments on reporting greenhouse gas (GHG) emissions.