Against the background established in the last three Parts, we can now assess the merits of the United States' practice of taxing on the basis of citizenship, with a particular focus on the United States' policy of taxing its nonresident citizens on their respective worldwide incomes and assets. In this Part, I evaluate citizenship-based taxation in terms of the benefits associated with U.S. citizenship. Governmentally furnished benefits are a traditional consideration for tax policy and, as we have seen, 130 is the rationale of Cook. However, upon examination, the benefits rationale for citizenship-based taxation proves unpersuasive, both in theory and in practice. The most significant civil and social benefits extended by the U.S. polity are tied to U.S. residence, not to U.S. citizenship.The strongest benefits argument for citizenship-based taxation is one with which citizenship mavens are most uncomfortable, namely, the Tiebout/purchase characterization of citizenship as a public service purchased through tax payments. However, even that approach cannot be squared with the current system, which in practice charges different tax prices (often radically different tax prices) for the identical benefits of U.S. citizenship, depending upon the level and kinds of taxes assessed by the nation in which a U.S. citizen resides and earns his income.