Digital implementation of the Once-Only Principle (OOP) reduces the administrative burden of accessing public services and enhances public administration performance. It also facilitates the mobility of citizens and businesses within the European Union through legal and effective EU-wide evidence. However, despite the existence of several semantic standards, a lack of an ontology for EU-wide evidence persists, primarily due to the low level of EU harmonisation of information that may prove compliance with procedural requirements. Building EU-wide evidence involves several cross-border communities of practice, composed of experts with different technical, legal, organisational, semantic, idiomatic and cultural backgrounds, spanning various public administration levels and sectors. This diversity introduces a range of cross-border, socio-technical challenges that have not been directly addressed in existing literature or by European projects and initiatives. Based on the lessons learned from the Digital Europe for All (DE4A) large-scale pilot project, the DE4A EU-wide OOP Semantic Elicitation Framework (DEOSEF) is proposed to guide business and semantic experts in the elicitation of EU-wide evidence for target public services, through a collaborative, context-aware, and iterative agile process involving diverse communities of practice. This paper presents DEOSEF as a foundational step for future initiatives involving a combined semantic elicitation-creation of EU-wide evidence.