This paper aims to define a high-resolution model to estimate nitrous oxide (N2O) emissions from the application of fertilisers to agricultural soils across the Republic of Ireland and to assess the implications for this approach on the assessment and mitigation of greenhouse gases (GHG) emissions. N2O emissions from the management of agricultural soils represented 10% of the total national GHG emissions in 2020. The high-resolution model proposed here modifies the current methodology based on the Guidelines for National Greenhouse Gas Inventories (IPCC, 2006) by adding soil characteristics and climate (environmental factors). To apply the high-resolution model, we use farm level microdata from the Teagasc National Farm Survey (NFS) and high-resolution spatial climate-based data over the 2014 to 2020 period. Results from the high-resolution model indicates a reduction of 3% in N2O emissions compared to the baseline model (IPCC methodology). However, the difference in estimated N2O emissions on individual farms can range from -45% to +40%. The carbon cost estimated by taking the high-resolution model results ranges from 20 to 150 euros per hectare, depending on local environmental factors. The design of a high-resolution emissions estimation process allows analysis of different agricultural practices and can assist in targeting appropriate GHG based mitigation measures based on cost-effectiveness criteria.