Achieving API efficiency: The case for a harmonised universal API stack in European payments

Abstract

This paper proposes a two-pillar model for a harmonised universal application programming interface (API) stack for European payments. Pillar 1 is a common, service-oriented API layer that decouples access channels from bank services. It standardises functional capabilities and data, and separates channel-specific customer authentication from authentication/authorisation of technical client systems. Once implemented, the same payment and data services can be consistently exposed to online channels, customer systems and external partners. The result is lower time-to-market, simplified compliance and scalable multi-channel distribution, determined by product value and risk, rather than integration constraints. Pillar 2 enables scheme and region-governed overlays; commercial terms and value-added services that build on the common layer without breaking interoperability. Schemes provide further scoping through implementation guides and extensions for routing, directories, aliases, test suites, certification, service-level agreements, liability frameworks and change control. A subsidiarity principle preserves local policy autonomy while the shared core ensures cross-border coherence. The model is a greenfield target architecture requiring phased migration, interoperability bridges and deprecation timelines. Its feasibility is reinforced by existing practice: the Berlin Group openFinance API Framework, used by around 80 per cent of European banks and nearly all third-party providers, already incorporates key elements and is expanding to card and wallet use cases. The two-pillar approach offers a pragmatic path to efficiency, innovation and supervisory clarity at a pan-European scale. This article is also included in The Business & Management Collection which can be accessed at http://hstalks.com/business.