The Universal Postal Union (UPU) is the United Nations special agency that coordinates the international mail system. At its inception in 1875 the UPU eliminated the use of accounting for mail flows between member countries as a means of reducing mundane transaction costs (Richardson & Kilfoyle, 2009). This situation continued until 1969 when transfer pricing (terminal dues) for the delivery of mail exchanged and services provided between countries was introduced. This article explains the use of accounting by the UPU to coordinate the international postal system drawing on a neglected aspect of evolutionary economics (“routines-as-truce”). Specifically, we show that the original accounting rules had distributional consequences within the organization, that knowledge to reform the rules was available but not fully incorporated into revised rules, and that the evolution of the rule provided a “quasi-resolution” of the conflict that motivated the rule change. The case explores the institutional work used to maintain the original “no accounting” rule and to bring about institutional change to allow the use of accounting in the management of international postal flows.