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

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

The OOTS implements the 'once-only' principle, whereby public administrations should not request data from users that has already been provided and can be reused securely and lawfully. However, applying this principle at a European level requires 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, also known as the Single Digital Gateway. This regulation establishes 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 available entirely in digital format.

The OOTS provides the technical infrastructure to support the automated exchange of documents and data between public authorities in different countries in relation to these procedures.

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

• EDelivery: Secure infrastructure for the exchange of messages between public entities.

• EID: Electronic identification mechanism with cross-border recognition.

• Evidence Broker: The component responsible for matching different types of evidence and documents issued across Member States.

Information sharing only takes place with the explicit consent of citizens or businesses. 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, which is an essential component for cross-border electronic authentication of citizens and businesses. This progress put the country at a significant stage in the OOTS implementation process.

The Agency for the Technological Reform of the State (ARTE) is responsible for national coordination of the Single Digital Gateway and represents Portugal in the European Commission’s Gateway Coordination Group.

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

The following month, 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 is an important step towards modernising public services and implementing the European Digital Single Market.

The “once-only” principle reduces the need for documents to be submitted repeatedly, thereby simplifying the relationship between citizens, businesses and public administration and promoting more efficient, interoperable, user-centred services.

The development of the system continues to accelerate at a European level. On 19 February 2026, the European Commission’s Gateway Coordination Group approved version 2.0 of the OOTS Technical Design Documents, which provide a structural update to the system's technical specifications. New features include extending the OOTS to new administrative domains, such as professional qualifications, driving licences and short-term rental procedures.

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