The financing of the UPU's activities is independent of the larger United Nations system. All budget expenses are financed jointly by the member countries, based on a contribution class system. Upon admission to the Union, new member countries are free to choose one of ten contribution classes ranging from one to 50 units.
An additional contribution class of one-half unit is reserved for the least developed countries. There are at present five countries with the maximum 50 contribution units.
Since 1992, the UPU has followed the practice of "zero growth", maintaining its annual budget at or below the level of inflation. The organization has the smallest annual budget in the UN system, amounting to approximately 37 million Swiss francs.