INITIATOR is a model that calculates all important nitrogen (N) and phosphate (P) fluxes in agricultural and natural ecosystems at national and regional scale. A key module in the INITIATOR model calculates manure production, manure application, livestock grazing, use of chemical fertilisers and the associated ammonia emissions, and uses these to determine the spatial distribution of manure application and ammonia emissions. These data are used as inputs to the AERIUS model and the National Water Quality Model (LWKM) for policy support activities such as the evaluation of the Manure Act (EMW) and for the Pollutant Release and Transfer Register (PRTR). This report reviews the quality requirements that Status A models have to meet. It summarises the theoretical basis of the INITIATOR model and the technical documentation, and describes the tests, validation and sensitivity analysis of the model.