This report analyses the impact of the IMO's decision to reduce the global limit on sulphur in marine fuels from 2020, which has the potential to be hugely disruptive to the shipping and oil product markets. The study analyses the different compliance options available for shippers. It provides Wood Mackenzie's forecast for the impact on oil product demand, crude and product pricing, and refining margins, with clear explanations of the assumptions made. The implications of an alternative full-compliance scenario are also described. The report provides a basis for refiners, shippers, crude producers, bunkering operators, investors and regulators to identify the implications of the legislation and the uncertainties it creates. The study is based on our detailed asset-level refinery modelling, economic forecasting and cross-fuel analysis. It draws upon the expertise of a global team of analysts who have conducted many conversations with market participants on this topic in recent years.