This article examines the link between universality aspirations of international organizations and member state funding by focusing on the United Nations system. Centering on financial input as a key proxy for ownership and collectively shared responsibility, we show that the UN Scale of Assessments has provided a surprisingly stable formula for calculating obligatory membership fees in the regular budgets of the UN Secretariat, Specialized Agencies, and other UN entities. We argue that the Scale of Assessments embodies a commitment to differentiated universality as it applies to all member states while considering key differences among them, notably their levels of per capita income and debt burden. While large parts of UN budgets currently depend on voluntary contributions by a small number of wealthy member states and thus stray far from universality ambitions, we suggest that assessed contributions are an underexploited tool for operationalizing multilateral universality in an uneven world. We propose four concrete measures for strengthening and expanding the use of assessed contributions that can contribute to making the UN system a more universally owned set of international organizations.