The Once-Only hub.Unlocking the full potential of the Single Market.
Welcome to the Once-Only Hub, a single environment providing reliable information and services relating to the Once-Only Technical System.
The Once-Only Technical System lets EU public authorities securely exchange official documents and data at the request of citizens and businesses as part of cross-border administrative procedures, e.g., when registering an address or vehicle when moving abroad. This innovative system eliminates the complicated manual search, mapping, and fetching of data between Member State authorities, improving efficiency, making people's lives easier, and reducing the costs of mobility in the Single Market.
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Introduction to the Once-Only Technical System (OOTS)
The Once-Only Technical System is a technical framework for data sharing. As of the end of 2023, citizens and businesses will be able to request official documents (known as “evidence”) to complete administrative procedures allowing people to study, work, live and retire in other EU countries in 7 simple steps. The decentralised architecture connects public authorities, so they can exchange evidence at the citizen's or business' request.
Discover the 21 procedures covered by the SDG Regulation in the scope of Once-Only Technical System and how EU citizens and businesses can benefit from Once-Only Technical System.
Once-Only Technical System - user journey for cross-border procedures
The user-journey refers to the steps anyone, a citizen or business, must take when using the Once-Only Technical System with a mind to the overall experience the user has.
Once-Only Technical System architecture
The Once-Only Technical System architecture adopts a decentralised approach, integrating and connecting systems through an interoperability layer using reusable "Building Blocks".
OOTS Guidance Presentation
The Guidance Presentation provides a useful introduction for teams across the EU working on the implementation of the Once-Only Technical System.
Once-Only Technical System Projectathons
Since 2023, the Commission has been organising Once-Only Technical System Projectathons. These are three-day events where national teams connect various systems and perform a marathon of peer-to-peer interoperability and compliance tests in a structured environment.
Discover more details about Projectathons and explore the steps you need to take to actively participate in the upcoming Projectathons.
Common and supporting services
To provide comprehensive support and proper exchange of evidence between Data Services and Online Procedure Portals, the Once-Only Technical System uses Once-Only common services and additional supporting services.
Technical design documentation
The technical and operational specifications of the Once-Only Technical System, are complemented by detailed, non-binding technical design documents jointly prepared by the Commission and Member States.
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SDG Once-Only Collaborative Space
In the context of the Once-Only Technical System, the mission of this group is to coordinate the implementation work around the setup of the Once-Only Technical System. The members of this group are the Member States (and other public entities). This groups is only accessible by representatives of the Member States (and other public entities).
Sub-groups
Six sub-groups have been set-up to examine specific topics related to the Once-Only Technical System and are expected to report to the Single Digital Gateway Coordination Group. They enable the participation of all Member States in the discussion and ensure the work done by Member State experts is monitored. The sub-groups can only be joined by experts officially nominated by their National Coordinators.
OOTS Projectathon collaborative space
The objective of this space is to encourage dialogue and exchange of ideas between stakeholders in an open and transparent environment. It will mainly serve to promote the Implementers Café series in preparation of the Projectathons. Space users should be implementers of the Once-Only Technical System.
Service desk
The Service Desk helps users improve the performance, continuity and reliability of their Once-Only Technical System implementations.
Once-Only Technical System in use
Projectathons
Number of Member States participating in OOTS Projectathons.
Common Services
Number of Member States connected to Commission-provided Common Services.
Testing Services
Number of Member States connected to Testing Services.