Historical content refers to IMERS generations 1 and 2.
The first generation, created in 2007, introduced the idea of simultaneously addressing shipping emissions and climate financing through a fund. It was based on a charge or levy on shipping emissions, linking the levy to an emission target or cap, and direct collection of the levy from ships. This was referred to as a cap-and-charge or hybrid scheme, in various submissions and reviews (IMO 2007b, IMO 2008b, UNFCCC 2008, Faber and Rensma 2008, Stochniol 2008).

The second generation, created in 2008-2009, implemented differentiation based on final destination of goods aiming to address concerns of developing countries. It also linked the levy to an external carbon price rather than a cap on emissions. Furthermore, it provided options to make the proposal more politically acceptable to some developed countries, including an option of collecting the levy as a pre-payment in a country that may not agree to a global levy collection (Haites 2008, Stochniol 2009a, GLCA 2009, QinetiQ 2009).

The third generation, in 2009-2010, created and integrated the rebate mechanism, thus replacing the complex differentiation based on final destination of goods. It also implemented a price ceiling and floor for the levy, and simplified fuel consumption reporting, among other improvements outlined above (IMO 2010a, IMO 2010b, IMO 2010c, ICTSD 2010).