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We show in this article that the way in which wealth is held within couples has profoundly changed during the period 1998-2010, leading to an individualisation of wealth and an increase in wealth inequality within couples. This development goes in hand with major changes in the lifestyles of couples: the generalization of out-of-wedlock cohabitation, the expansion of PACS civil partnerships as an alternative to marriage, and the more frequent use of marriage contracts, which is resulting in the separation of assets within households. We then show that this trend towards the individualisation of wealth-holding within couples has not been taken into account in the tax system, which tends to assume that resources are pooled within households. This phenomenon calls for a re-examination of the principles of justice that underlie the taxation of the wealth of couples, whether that takes place in respect to income or the possession or transmission of assets. Current taxation is inconsistent in the tax treatment of couples. The purpose of this article is to document this state of affairs and to open up avenues for reflection. JEL classification: D31, H31, J12