<p>It is interesting to note that the theory of comprehensive income taxation often refers to ability to pay without specifying precisely whose ability is meant: that of the individual or that of the family. It is obvious that each person is socially and morally committed to other individuals-notably vis-a-vis parents or children. This usually leads to intra-household transfers of income which must affect the individual ability to pay of each family member. The problem of income-sharing in the family is, however, often ignored in the literature.</p>