Note that additional commentary on the issues discussed in this Practice Note in the context of the regulation, consenting and incentivisation of the net zero energy transition is available in the following textbook that we have published: Collinson and Hockman on Energy Law: Regulating, Consenting and Incentivising the Energy Transition. This Practice Note provides an overview of the proposed Gas Shipper Obligation (GSO), a levy on licensed gas shippers in Great Britain (‘GB’). It explains what the GSO is and sets out its legal basis, territorial scope, who will administer it, how it will be calculated and charged, what credit support requirements it will entail, what exemptions might be available, and how it will interact with low carbon hydrogen production and blending. It also sets out the key policy developments shaping the design of the GSO and considers the practical implications for market participants. What is the GSO? The GSO is a proposed levy on licenced gas shippers (Gas Shippers), who are located in GB. In the future, the GSO may be extended to Northern Ireland