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Commission releases version 2.0 of the OOTS Technical Design Documents

5 March 2026 | 2 minutes read

On 19 February 2026, the Gateway Coordination Group of the Single Digital Gateway adopted, by consensus, version 2.0 of the Technical Design Documents (TDDs) of the Once-Only Technical System (OOTS) as the next major version of the OOTS specifications.

Implementing Regulation (EU) 2022/1463(opens in a new tab) sets out the technical and operational specifications of the Once-Only Technical System. These specifications are complemented by detailed, non-binding documents, known as OOTS Technical Design Documents. These Technical Design Documents provide a high-level overview of the main components of the Once-Only Technical System, describe their functionality, and outline the process for exchanging documents and data through the system.

The objectives
of the 2.0 release are to:

  • Provide full coverage for all requirements from OOTS implementing regulation;
  • Provide a comprehensive, future-proof feature set;
  • Support requirements from Evidence Mapping subgroup and its approach to mapping;
  • Support adoption of structured evidence types based on OOTS data models;
  • Adopt SMP and other advanced eDelivery features;
  • Provide additional security profiling, leveraging expertise from security subgroup of the Single Digital Gateway coordination group;
  • Reflect implementation experience from past few years: clean up deprecated features;
  • Enable OOTS for procedures related to professional qualifications, driving licenses and short-term rental;
  • Provide the foundation enabling large-scale OOTS roll-out in the coming years;
  • Enable EUDI synergies and prepare for eIDAS-2.

This update consists of several new content additions, revisions and corrections and is not backwards compatible with previous versions. The release is publicly available:

In addition to TDD 2.0, a maintenance patch release 1.2.4 was released. It enables continued use of the current minor version 1.2 of the OOTS specifications. This patch backports some of the code list updates of the new TDD release 2.0. It is also available on code.europa.eu(opens in a new tab).

For more information on how Europe is going ‘Once-Only’, visit the Once-Only hub(opens in a new tab).