To ensure an efficient payment system, it is important to maintain competition among payment service providers, but data available to gauge the degree of competition are quite limited. The authors propose and implement a frontier-based method to assess relative competition in bank-provided payment services. Billion dollar banks account for around 90 percent of assets in the U.S., and those with around $4 to $7 billion in assets turn out to be both the most and the least competitive in payment services, not the very largest banks.