Definitions provided in the amended Regulation MRV ETS 2015/957 and FEUM Regulation EU 2023/1805, although similar, the responsibilities differ. Under EU ETS, the ultimate liability for compliance rests either with the Registered Owner or with the ISM company through a specific mandate in place. In contrast, under FEUM regulations, the responsibility for compliance lies with the ISM company, specifically the Document of Compliance (DOC) holder of the ship.