This paper focuses on the huge differences in old-age pension taxation within and across OECD countries and highlights fiscal equity and efficiency issues that emerge in a world of internationally mobile workers and pensioners. It highlights that pension taxation differs widely not only across countries but also across pension pillars within a country, creating savings and mobility distortions and fiscal equity problems at individual and country level. The paper offers explanations for this heterogeneity and proposes a switch from deferred taxation towards front-loaded taxation of retirement savings to meet the demographic challenges of a globalized world. Three policy options presented differ in the way taxes are paid, but all of them are claimed superior to single-country measures taken to uphold deferred pension taxation or to rely on renegotiations of bilateral double taxation treaties.