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.
Video
Watch this video to learn more about Once-Only.
Introduction to the Once-Only Technical System (OOTS)
The Once-Only Technical System (OOTS) is a framework designed to facilitate data sharing across borders. It will allow citizens and businesses to request official documents, or "evidence," needed for administrative procedures, thus making it easier for them to study, work, live, or retire when moving between EU countries. The system’s 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.
Projectathon #6
The June 2025 Projectathon will support Member States that are (nearly) production-ready to enable end-to-end transactions, while assisting those catching up to enhance their technical readiness or retest the updates to their systems. This Projectathon will also support the onboarding of competent authorities, in particular those in the population, education and business domains as well as those interested in testing and/or close to going live.
Projectathon #5
The November 2024 Projectathon was a thematic event with a focus on Vehicle Registries and Business-related procedures, targeting this specific set of Competent Authorities.
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.
Latest news
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Member States take stock between milestone events in #14 OOTS Implementers Café (OOTSHUB) —https://ec.europa.eu/digital-building-blocks/sites/download/attachments/894304673/illu-news-oots-24-04-2025.jpg
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Watch Once-Only Studio interview with Finnish SDG team (OOTSHUB) —https://ec.europa.eu/digital-building-blocks/sites/download/attachments/891322871/illu-news-oots-08-04-2025.jpg
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Major success as Member States and Competent Authorities gather in Vilnius, Lithuania (OOTSHUB) —https://ec.europa.eu/digital-building-blocks/sites/download/attachments/894304266/illu-news-oots-18-04-2025.jpg
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Once-Only means a simpler, more resilient digital environment in Europe (OOTSHUB) —https://ec.europa.eu/digital-building-blocks/sites/download/attachments/892470445/illu-news-oots-16-04-2025.jpg
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Citizen forums show how the Once-Only Technical System can save students time and money (OOTSHUB) —https://ec.europa.eu/digital-building-blocks/sites/download/attachments/887384412/illu-news-oots-01-04-2025.jpg
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Once-Only goes local, 2025 (OOTSHUB) —https://ec.europa.eu/digital-building-blocks/sites/download/attachments/887383475/illu-news-oots-27-03-2025.jpg
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Digital Commission Awards: Once-Only wins for Team demonstrating the most multidisciplinary approach for digital-ready policymaking (OOTSHUB) —https://ec.europa.eu/digital-building-blocks/sites/download/attachments/887382196/illu-news-oots-19-03-2025.jpg
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Lithuania prepares to roll out the Once-Only Technical System (OOTSHUB) —https://ec.europa.eu/digital-building-blocks/sites/download/attachments/887381888/illu-news-oots-18-03-2025.jpg
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General Report on the Activities of the EU 2024 shows value of “Once-Only” (OOTSHUB) —https://ec.europa.eu/digital-building-blocks/sites/download/attachments/887381485/illu-news-oots-14-03-2025.jpg
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Germany progresses on national-Once-Only Technical System (OOTSHUB) —https://ec.europa.eu/digital-building-blocks/sites/download/attachments/887380245/illu-news-oots-06-03-2025.jpg
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How Europe will go “Once-Only” in 2025 – updates from 13th Implementers’ Café (OOTSHUB) —https://ec.europa.eu/digital-building-blocks/sites/download/attachments/883824996/illu-news-oots-20-02-2025.jpg
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2025 Commission work programme puts simplification in the spotlight (OOTSHUB) —https://ec.europa.eu/digital-building-blocks/sites/download/attachments/883824247/illu-news-oots-17-02-2025.jpg
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"Once-Only" steers Europe towards simpler cross-border processes for a better Single Market, in line with the EU Competitiveness Compass (OOTSHUB) —https://ec.europa.eu/digital-building-blocks/sites/download/attachments/881983974/illu-news-oots-07-02-2025.jpg
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Register now: Europe goes Once-Only - Lithuania edition (OOTSHUB) —https://ec.europa.eu/digital-building-blocks/sites/download/attachments/881983883/illu-news-oots-06-02-2025.jpg
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Gateway Coordination Group discusses Once-Only in the year ahead (OOTSHUB) —https://ec.europa.eu/digital-building-blocks/sites/download/attachments/881983728/illu-news-oots-05-02-2025.jpg
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Commission launches development of new Technical Support Dashboard (OOTSHUB) —https://ec.europa.eu/digital-building-blocks/sites/download/attachments/875855875/illu-news-oots-24-01-2025.jpg
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Single Market Strategy 2025 Call for evidence January 2025 (OOTSHUB) —https://ec.europa.eu/digital-building-blocks/sites/download/attachments/864335488/illu-news-oots-07-01-2025.jpg
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Webinar on eDelivery value proposition: national experiences. 3 April 2025 (eDelivery User Community) —
3 April 2025
eDelivery value proposition: national experiences
Discover the eDelivery service offering and the advantages of adopting eDelivery. This is an opportunity to discover success stories from some of the Member States that adopted eDelivery. Reach out to share also your story.
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How-to video on Domibus 5.1 and 5.2 new features. Available in Q4 2025 (eDelivery User Community) —
Q4 2025
How-to video on Domibus 5.1 and 5.2 new features
The "new features in Domibus 5.1 and 5.2" how-to video will guide the users through the new features of Domibus, which is the sample implementation of an eDelivery Access Point maintained by the European Commission.
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eDelivery Interoperability Forum. 16 October 2025 (eDelivery User Community) —
16 October 2025 | 10:30-12:30 (CEST)
eDelivery Interoperability Forum: 2025 review
Sign up if you are not yet a member of our forum of eDelivery solution providers.
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eDelivery Interoperability Event. 16 September 2025 (eDelivery User Community) —
16 September 2025 | TBC
eDelivery Interoperability Event. 16 September 2025
The collaboration between eDelivery and software providers within the the Interoperability Event has the goal of testing the updated eDelivery AS4 2.0 draft specifications, with a focus on the new cryptography.
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Webinar on eDelivery Trust Models. 19 June 2025 (eDelivery User Community) —
19 June 2025
Webinar on Trust Models used in eDelivery
We will present Trust Models used in eDelivery. This will be for both those who are interested in using eDelivery and those who would like to better understand Trust Models to assess how these suit their purpose in a particular scenario.
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New study shows how Once-Only can reduce administrative burden for EU SMEs and self-employed workers (OOTSHUB) —https://ec.europa.eu/digital-building-blocks/sites/download/attachments/807043131/illu-news-oots-30-09-2024.jpg
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CEF Building Blocks Presented at Internet of Things (IoT) World Congress 2018 (Digital) — The current lack of ICT platform standards to manage such information means an obstacle for the development of Smart Digital Services.
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Connecting Europe: CEF Building Blocks Presented at eDelivery Day in Sweden (Digital) — Sweden has made significant progress in the deployment of eDelivery infrastructure at the creation of a vibrant digital ecosystem around it.
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CEF Building Blocks Presented at the Swedish Conference eFÖRVALTNINGSDAGARNA (Digital) — The event ran over two days, filled with the latest information regarding e-government and digital transformation.
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CEF Building Blocks Presented at the German Federal Office of Administration (Digital) — The BVA has a history of close cooperation with the European Commission, and Member States' authorities.
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CEF eInvoicing and eDelivery presented at the Exchange Summit in Berlin (Digital) — The European Commission presented eInvoicing at the Exchange Summit in Berlin
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Lithuania hosted an eInvoicing workshop (Digital) — To prepare for the upcoming Directive 2014/55/EU deadline, the Lithuanian government hosted an eInvoicing workshop
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CEF eTranslation Presented at Translating Europe Forum 2018 (Digital) — CEF eTranslation aims to help European and national public administrations exchange information across language barriers in the EU.
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CEF eDelivery and eInvoicing workshop at the Danish Business Authority (Digital) — What does digital invoicing and infrastructure of the future look like?
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CEF Context Broker Presented at the European Week of Regions and Cities (Digital) — EWRC is an annual four-day event during which cities and regions showcase their capacity to create growth and jobs
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Tuesday 26th of July - Live Webinar: "CEF eDelivery - What's In It For You?" (Digital) — Thank you to all who attended the webinar. We hope it proved useful in clarifying your understanding. For those of you who couldn't attend, or who wish to re-listen, below you will find recordings of each segment of the webinar.
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CEF eSignature Presented at ETSI eSignature and eSeal Validation Workshop (Digital) — The one-day workshop discussed standardisation for eSignature/eSeal Validation services provided by Trust Service Providers, addressing conformity assessment, protocols and validation report.
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CEF Telecom call 2 virtual Info Day 2016 (Digital) — The 2016 CEF Telecom call 2 virtual Info Day will take place on Friday 3 June 2016 and will cover four priorities of the 2016 CEF Telecom Calls.
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Information session on AS4 (Digital) — The Information Session was primarily aimed at software vendors, system integrators, implementers and training providers interested in AS4
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CEF Telecom Call 2 virtual Info Day, 3 June 2016 (Digital) — Up to EUR 70 million is foreseen from the 2016 CEF Telecom Work Programme for grants managed by INEA
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CEF Digital 2018 at the Trust Services Forum 2016 (Digital) — Today the European Commission Directorate General for Informatics (DIGIT) presented a state-of-play of the CEF building blocks to the ENISA Trust Services Forum 2016.
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EESPA General Assembly 2016 (Digital) — CEF Digital 2018 presented eInvoicing at the EESPA general assembly meeting on 19 May in Tallinn, Estonia
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Register now for the fifth annual conference on innovative public procurement (Digital) — The European Commission is organizing a conference focusing on public procurement of innovation and the potential of innovative procurement on 26 October in Berlin.
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Information session on the AS4 (Digital) — The European Commission is holding a half day information session on Thursday 26 May for software vendors, system integrators, implementers and training providers interested in AS4
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CEF eDelivery and eInvoicing DSI Stakeholder Days (Digital) — We invite you to be part of the CEF eDelivery & eInvoicing Stakeholder Days, which are to be held on 29 November – 1 December 2016
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eDelivery Extended Expert Group Workshop (Digital) — Members of the Extended Expert Group concluded that the CEF eDelivery building block is a key enabler of the EU's Digital Single Market.
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CEF eID Presented at the FIDO Alliance (Digital) — CEF eID helps public administrations and private online service providers to easily extend the use of their online services to citizens from other EU Member States
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Trust Services Forum 2016 (Digital) — ENISA, in collaboration with the European Commission eIDAS Task Force, is organizing, for the second consecutive year, the Trust Services Forum 2016.
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Update: Information session on AS4 (Digital) — The European Commission is holding a half day information session on Thursday 26 May 2016
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CEF Digital 2018 at CeBIT 2016 in Hannover, Germany (Digital) — CEF Digital 2018 made its second appearance at CeBIT with a booth entitled "Digital Public Service across Borders" positioned in the Public Sector Park hall.
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Reusable Components at DIGITEC 2016: Digital Future (Digital) — The IT Departments of the European Commission (DIGIT) and the European Parliament (ITEC) have joined forces to organise DIGITEC 2016: Digital Future.
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CEF Digital 2018 Presented at the Agency for Administrative Modernisation (Digital) — The event consisted of representatives from both the public and private sectors, including municipalities, government ministries, as well as consulting and IT companies
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11th eDelivery Informal Cooperation Network Meeting. 26 November 2024 (eDelivery User Community) —
26 November 2024
11th Informal Cooperation Network meeting
The eDelivery ICN is a platform for Member State representatives who are involved in the set-up of national eDelivery infrastructure to actively contribute to the adoption of eDelivery at national and EU levels.
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12th eDelivery Informal Cooperation Network Meeting. 7 May 2025 (eDelivery User Community) —
7 May 2025 | Full day
12th Informal Cooperation Network meeting
The eDelivery ICN is a platform for Member State representatives who are involved in the set-up of national eDelivery infrastructure to actively contribute to the adoption of eDelivery at national and EU levels.
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eDelivery Interoperability Forum. 27 February 2025 (eDelivery User Community) —
27 February 2025 | 10:30-12:30 (CET)
eDelivery Interoperability Forum: plans for 2025
We are going to give you an update on the profile specifications changes in 2024 and preview what is next when it comes to eDelivery profile 2.0 adoption. Sign up if you are not yet a members of our forum of eDelivery solution providers.
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eDelivery Interoperability Forum. 24 October 2024 (eDelivery User Community) —
24 October 2024
eDelivery Interoperability Forum: road to profiles 2.0 adoption
We shared the updated drafts of the profile specifications, announced public consultation on the potential inclusion of a new feature in the AS4 2.0 profile, and our DG DIGIT colleague presented EMSWe, an eDelivery digital ecosystem.
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Bookmark your calendars! Upcoming events in Q1 and Q2 of 2025 (OOTSHUB) —https://ec.europa.eu/digital-building-blocks/sites/download/attachments/886439987/illu-news-oots-04-03-2025.jpg
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National eDelivery implementations in action: recording now available (Digital) — Our webinar spotlighted national implementations from Denmark, Slovenia and Norway. We thank all the participants, speakers and attendees for their time and insights, and we invite everyone who missed the live session to watch the recording.
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Discussion on public consultation on uncompressed payload non-repudiation. 28 November 2024 (eDelivery User Community) —
28 November 2024
Discussion on uncompressed payload non-repudiation
This was an opportunity for stakeholders to actively engage in order to help make an informed decision about whether to add the uncompressed payload non-repudiation feature to eDelivery AS4 2.0 and, if so, which variants should be supported.
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National Once-Only journeys on show during the #5 OOTS Projectathon (OOTSHUB) —https://ec.europa.eu/digital-building-blocks/sites/download/attachments/845479964/illu-news-oots-28-11-2024-filter.jpg
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Member States debrief November Projectathon in OOTS Implementers Café #12 (OOTSHUB) —https://ec.europa.eu/digital-building-blocks/sites/download/attachments/853082211/illu-news-oots-18-12-2024-02.jpg
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Commission publishes event report for the #5 Once-Only Technical System Projectathon (OOTSHUB) —https://ec.europa.eu/digital-building-blocks/sites/download/attachments/853082145/illu-news-oots-18-12-2024.jpg
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Live demo proves the reusability of OOTS Common Services for the EUDI Wallet at Contact Group meeting (OOTSHUB) —https://ec.europa.eu/digital-building-blocks/sites/download/attachments/839417996/illu-news-oots-26-11-2024.png
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EU Member States and competent authorities make significant progress on Once-Only in Helsinki Finland (OOTSHUB) —https://ec.europa.eu/digital-building-blocks/sites/download/attachments/822050890/illu-news-oots-25-10-2024.jpg
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Webinar on eDelivery: intro, value and success stories. 28 September 2023 (eDelivery User Community) —
28 September 2023 | Past event
Webinar on eDelivery: intro, value and success stories
In this webinar, users will discover the eDelivery service offering and the advantages of adopting eDelivery...
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DomiSMP 5.0 video guides. Released on 19 March 2024 (eDelivery User Community) —
19 March 2024
How-to video on DomiSMP 5.0 new features
This video will guide you through the use and possibilities of DomiSMP, the sample software provided by the European Commission to implement an eDelivery Service Metadata Publisher for publishing and retrieving data.
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OECD recommends streamlining and improving services through Once-Only (OOTSHUB) —https://ec.europa.eu/digital-building-blocks/sites/download/attachments/840269998/illu-news-oots-27-11-2024.jpg
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eDelivery Interoperability Event. 11 & 25 June, 1 October 2024 (eDelivery User Community) —
11 & 25 June, 1 October 2024
Interoperability Event for testing AS4 specifications
The collaboration between eDelivery and software providers within the the Interoperability Event has the goal of testing the updated eDelivery AS4 2.0 draft specifications, with a focus on the new cryptography.
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eDelivery presentation at ENTSOG's Data Exchange and Cybersecurity Workshop. 29 October 2024 (eDelivery User Community) —
29 October 2024
ENTSOG's Data Exchange and Cybersecurity Workshop
A presentation titled "eDelivery rationale for AS4 updates" by Bogdan Dumitriu opened the AS4 panel on day 1. This session explored the latest developments and updates in AS4, critical for secure data exchange.
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The 5 OOTS Projectathon closes with an increased number of more complex tests than ever (OOTSHUB) —https://ec.europa.eu/digital-building-blocks/sites/download/attachments/837451895/illu-news-oots-22-11-2024.jpg
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Slovakia makes great progress in its national OOTS implementation (OOTSHUB) —https://ec.europa.eu/digital-building-blocks/sites/download/attachments/832700420/illu-news-oots-14-11-2024.jpg
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Discover country-specific pages in the Once-Only Technical System Evidence Explorer (OOTSHUB) —https://ec.europa.eu/digital-building-blocks/sites/download/attachments/829096058/illu-news-oots-07-11-2024.jpg
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Request tailor-made training session to support your OOTS implementation (OOTSHUB) —https://ec.europa.eu/digital-building-blocks/sites/download/attachments/824770774/illu-news-oots-30-10-2024.jpg
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eDelivery Interoperability Forum. 18 April 2024 (eDelivery User Community) —
18 April 2024
eDelivery Interoperability Forum: AS4-conformant solutions
In the second community meeting this year, we focused on the eDelivery AS4-conformant solutions and their new listing on our website. To keep this relevant, dear product and service vendors, please share updated information about your software.
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eDelivery Interoperability Forum. 29 February 2024 (eDelivery User Community) —
29 February 2024
eDelivery Interoperability Forum: updated eDelivery 2.0 profiles
Collaboration between eDelivery and software and service providers continues in 2024. We discussed the disposition of review comments resulting from the recent public consultation, and presented the updated versions of the eDelivery profiles.
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EU Member States and the Commission gear-up for the November 2024 OOTS Projectathon (OOTSHUB) —https://ec.europa.eu/digital-building-blocks/sites/download/attachments/819920973/illu-news-oots-22-10-2024.jpg
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Webinar on using Dynamic Discovery with Domibus. 26 September 2024 (eDelivery User Community) —
26 September 2024
Webinar: Using Dynamic Discovery with Domibus
We showed you how to use Dynamic Discovery in an eDelivery network based on our SMP and BDXL profiles, the specifications for publishing and locating service metadata within a 4-corner network, respectively.
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Commission publishes Once-Only Technical System Acceleratormeter (OOTSHUB) —https://ec.europa.eu/digital-building-blocks/sites/download/attachments/809172996/illu-news-oots-03-10-2024.jpg
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Once-Only Technical System applies for Digital Commission Awards (OOTSHUB) —https://ec.europa.eu/digital-building-blocks/sites/download/attachments/808452948/illu-news-oots-02-10-2024.jpg
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Commission publishes Once-Only LCM onboarding procedure in training environment (OOTSHUB) —https://ec.europa.eu/digital-building-blocks/sites/download/attachments/804618289/illu-news-oots-25-09-2024.jpg
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Mario Draghi recognises value of 'Once-Only' for the Single Market (OOTSHUB) —https://ec.europa.eu/digital-building-blocks/sites/download/attachments/797933716/illu-news-oots-13-09-2024-V2.jpg
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Commission releases version 1.1.0 of the Technical Design Documents (OOTSHUB) —https://ec.europa.eu/digital-building-blocks/sites/download/attachments/797933692/illu-news-oots-13-09-2024.jpg
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Austria and its competent authorities advance significantly in publishing evidence types (OOTSHUB) —https://ec.europa.eu/digital-building-blocks/sites/download/attachments/796295322/illu-news-oots-11-09-2024-V2.jpg
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Dynamic Discovery webinar. 8 June 2023 (eDelivery User Community) —
8 June 2023
Webinar: Dynamic Discovery in an eDelivery network
We presented the use of Dynamic Discovery in an eDelivery network based on the eDelivery SMP profile, an open technical specification for publishing service metadata within a 4-corner network, and the eDelivery BDXL profile.
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Europe Goes Once Only Finland edition (OOTSHUB) —https://ec.europa.eu/digital-building-blocks/sites/download/attachments/796295214/illu-news-oots-11-09-2024.jpg
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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 the last OOTS Projectathon.
Common Services
Number of Member States connected to Commission-provided Common Services.
Testing Services
Number of Member States connected to Testing Services.