<p>This article develops and defends a novel argument for why individuals have a duty to contribute to the realisation of justice by making a productive contribution. Analysing the shortcomings of attempting to ground such a duty in either reciprocity or the idea of sharing burdens, I suggest that the best alternative is a hybrid account which draws on both. The account says that firstly, everyone must make an equally good effort, in relation to their ability, to contribute the socially necessary labour needed to realise a just state of affairs, where everyone receives what they are due. Secondly, if and when this level is reached, everyone has a conditional obligation to further benefit others, if they benefit from the additional work of others. Opting out is thus permissible, since this part is only triggered if one wants to take part of the social surplus produced by others.</p>