Portugal and the “once-only” principle in the European Union

The Once-Only Technical System (OOTS) allows citizens and businesses carrying out cross-border administrative procedures within the European Union to avoid having to resubmit documents or information already held by a public authority.

This model implements the “once-only” principle, according to which Public Administration should not request data from users that has already been provided and can be reused securely and lawfully. Applying this principle at European level requires, however, a high degree of technical, legal and organisational coordination between the information systems of the 27 Member States.

The legal framework: the Single Digital Gateway Regulation

The legal framework of the OOTS stems from Regulation (EU) 2018/1724, known as the Single Digital Gateway. This regulation establishes the creation of a single European portal for the digital provision of information, administrative procedures and support services for citizens and businesses. Among other obligations, it requires Member States to make the 21 procedures identified in Annex II fully available in digital format.

The OOTS is the technical infrastructure that supports the automated exchange of documents and data between public authorities in different countries within the context of these procedures.

Operational since December 2023, the system is based on three main components:

• EDelivery: Secure infrastructure for message exchange between public entities;
• EID: Electronic identification mechanism with cross-border recognition;
• Evidence Broker: Component responsible for matching different types of evidence and documents issued across Member States.

Information sharing only takes place with the explicit consent of the citizen or business. In each procedure, the user specifically authorises access to data held by another public authority.

Portugal’s role

Portugal was one of the first Member States to notify its eIDAS node, an essential component for the cross-border electronic authentication of citizens and businesses. This progress placed the country in a position of significant maturity in the OOTS implementation process.

National coordination of the Single Digital Gateway is ensured by the Agency for the Technological Reform of the State (ARTE), which represents Portugal in the European Commission’s Gateway Coordination Group.

In September 2025, Portugal hosted the initiative Europe Goes Once-Only — Portugal Edition in Lisbon, bringing together more than 300 technical specialists from across the European Union to discuss the practical implementation of the system.

In October 2025, the Directorate-General for Higher Education officially became an evidence provider within the OOTS, joining the European network for the automated exchange of documents relating to academic qualifications. It was one of the first Portuguese public entities to connect operationally to the system.

Digital transformation with a European dimension

Portugal’s participation in the OOTS represents an important step in the modernisation of public services and the implementation of the European Digital Single Market.

By reducing the need for repeated submission of documents, the “once-only” principle simplifies the relationship between citizens, businesses and Public Administration, promoting more efficient, interoperable and user-centred services.

The development of the system continues to accelerate at European level. On 19 February 2026, the European Commission’s Gateway Coordination Group approved version 2.0 of the OOTS Technical Design Documents, a structural update of the system’s technical specifications. Among the new features is the extension of the OOTS to new administrative domains, including professional qualifications, driving licences and procedures related to short-term rentals.

For 2026, the European Commission has also defined as a strategic objective the progressive connection of all national competent authorities to the OOTS, both as evidence providers and evidence requesters, consolidating the infrastructure as one of the pillars of European digital public administration.