The Maui C Sands reservoir contains most of the remaining gas-condensate reserves in the mature Maui Field. Technical and commercial management of a hydrocarbon producing field such as Maui relies heavily on the confidence in the forecasted production and reservoir performance and the associated uncertainties. This paper discusses how the key static and dynamic uncertainties can be identified, evaluated, and modelled to determine their impact on remaining reserves and further development options. The approach is based on the use of a combination of representative sector and full field dynamic models to establish the model sensitivities. A few models covering the range of uncertainties are then history matched in an iterative process whereby the uncertainty ranges are updated based on the history match results. Finally, production forecasts are generated for the history matched models to assess the range of reserves and to evaluate and optimise further development options. As a precursor to this, a single base case model is history matched and production forecasted whereby a statistical method is used to select the base case parameters and to assess the associated reserves uncertainty range.