During the late seventeenth century, Atlantic trade grew dramatically. The New Institutional Economists attribute this to institutional developments. During this period, Quakers emerged as the region's most prominent trading community. Some historians explain this achievement as the result of the competitive advantage that Quakers gained from their formal institutions for contract enforcement. This article studies the London Quaker community to show that, in fact, they only began to police the conduct of business regularly after 1750, as part of a wider effort to promote the Society's reputation. Formal institutional advantages cannot explain the Quakers’ early trading success.