This deliverable document reports on the ingredients required for a robust representation of uncertainties in the main building blocks of the CHE prototype anthropogenic CO2 emissions monitoring system including the prior, observation, model and methodological uncertainties. All components of this CHE prototype are considered here to provide a consolidated view on the characterisation of uncertainties. The individual components themselves are discussed in their respective reports: Observations in D5.2, emissions and transport models in D5.4, inversion / data assimilation methodology in D5.6 while D5.9 provides a synthesis of these building blocks for an end-to-end prototype system. The focus of this report is first to list the uncertainty components of the individual building blocks for the prototype and how they contribute to the overall posterior uncertainty estimations, second to identify tools and metrics to evaluate and benchmark the posterior uncertainty estimates of the prototype, and third to identify and prioritise the immediate development needs (to be achieved in the H2020 CoCO2 project) of the prototype with respect to the uncertainty representation as well as longer term research needs (potentially to be addressed in future Horizon Europe research calls) together with an estimate of the required efforts. The overall posterior uncertainty estimate of the CHE prototype arises from uncertainties in the prior data, the model uncertainty, uncertainties in the observations as well as from the ability of the inversion / data assimilation system to correctly provide the posterior uncertainty given the uncertainties of the before listed ingredients.