This article argues that the properly conceived fairness norm for taxation leads to a personal realization income tax. Fairness in taxation refers to “allocative tax fairness,” that is, the ethical/political standard according to which taxes are to be apportioned among the relevant population. In concrete terms, the standard constitutes the tax base for individual taxpayers. Allocative fairness is but one norm bearing on taxation, but it is one that (in academia, at least) has unjustifiably taken a back seat to economics and welfarist norms, largely due to the perception that allocative tax fairness lacks any specific content apart from the speaker’s political and personal tastes and, therefore, by implication, is without independent normative grounding. The short riposte is that exclusive adherence to economic and/or welfarist norms is itself a matter of personal taste. The more elaborate response entails showing that (1) fairness is an independent norm category apart from economics and welfarism; (2) allocative fairness matters in the construction of tax systems; and (3) allocative tax fairness has a discernable content. That content is conceptualized in the notion of “objective ability-to-pay,” which refers to an individual’s realized net increase in material wealth over the taxable period (reduced by off-the-bottom allowances), and does not refer to utility, satisfactions, or well-being as such. The tax base that conforms to the objective ability-to-pay principle is that of a personal realization income tax, as opposed to (say) a personal wealth, accretion, or consumption tax.