The simplest option is a direct payment to an emission account administered centrally. Each ship would have an account and would be liable for the levy being settled for the previous period. The account would be with the World Bank (or a selected commercial bank operating the accounts). The levy will be paid by charterers, ship-owners, ship-operators or other entities as specified in the commercial terms of the ship charter/use, in a similar way as the terms which specify who pays for fuel.
Compliance would be enforced through Port State Controls in Annex I countries only. They would have access to a central system for shipping emissions based on IMO ship numbers. There is no need to enforce the scheme in non-Annex I countries, which is an important co-benefit of the scheme as it accelerates implementation and avoids lack of capacity in some developing countries.
The governance of the funds, including a supra-national body and how the revenue would be distributed, is to be agreed within the climate change negotiations. This would be part of the overall framework for financing climate change action to be governed under the UNFCCC convention. The supra-national body is not prejudged but proposed at this stage. One reason is to assure that the funding generated is treated as additional in the meaning of the Bali Action Plan for climate change (i.e. it should be governed under the UNFCCC convention).