National Once-Only Technical System (OOTS) for cross-border and national exchange of evidence (data)

Video demo

In 2025. the European platform for cross-border electronic evidence exchange – OOTS (Once Only Technical System) became operational in the Republic of Croatia. Regulation (EU) 2018/1724 of the European Parliament and of the Council of 2 October 2018 establishing a single digital gateway to provide access to information, to procedures and to assistance and problem-solving services prescribes the obligation for each Member State to set up a national platform for evidence exchange.

According to the Regulation, evidence is any document or data required by a competent authority to confirm facts or compliance with the requirements for a procedure listed in Annex II of the Regulation.

Through the OOTS platform, we joined a unified electronic area that connects public administrations from various domains and removes mobility barriers at the level of the entire European Union.

The platform provides citizens and entrepreneurs with a better user experience when using electronic services, and it is expected to reduce costs and save time that users spend obtaining and translating evidence they must submit. By using the OOTS platform, users are able to request evidence directly from the competent authorities of another Member State (cross-border evidence exchange) by applying the Once-Only principle.

The platform consists of two main functional units:

• the ability to request evidence from other Member States, and
• the ability to deliver evidence to authorities of other Member States responsible for their electronic services.

The Regulation recognizes 21 key procedures for cross-border users. These procedures concern important life events such as birth, change of residence, studying, employment, retirement, and the establishment, management, and closure of businesses. All electronic services from the defined procedures are made available via the OOTS platform with the exception of the ones concerning vignettes.

Description of a simple process for using the OOTS platform:

When using the service, the user in any Member State logs into the selected electronic service using their electronic ID card or their electronic identity notified in accordance with the EU eIDAS Regulation.

After successful authentication, the electronic service allows the user to request the delivery of evidence via the OOTS system – directly from the competent authorities of another Member State. The user selects the type of evidence to be delivered, the Member State from which the evidence originates and identifies the competent evidence provider in the selected Member State.

Based on data from the e-Services, a request for evidence delivery is sent to the evidence provider through the OOTS system. If the evidence provider successfully matches the identity (the electronic identity of the user who requested the service and the identity of the user for whom the evidence is stored in their database or public register), the user is redirected to a preview area where they review the evidence and give consent for its delivery to the electronic service via the OOTS system. Evidence is exchanged directly between competent authorities of Member States, but only upon request and with the user’s consent.

The user’s consent initiates the exchange of evidence between different sectors and competent authorities of the public administration of individual Member States through the mentioned technical system. The public administration body providing the e-Services implicitly trusts the evidence delivered through OOTS, as it is provided directly by the competent authority via the secure communication channel of the national OOTS platform.

Connecting the OOTS to other existing EU data exchange networks, such as EESSI and EUCARIS is also planned.

For the integration of electronic services, the platform is integrated with the NIAS system and the e-Citizens system, and for the integration of evidence providers, services on the Government Service Bus (GSB) and data exchange access points in the competent authorities/institutions is used.

National application of the OOTS platform

In addition to supporting cross-border evidence exchange, the OOTS platform also supports the integration of national electronic services and evidence providers and is integrated with other platforms of the State Information Infrastructure and hosted in the Shared Services Center.

Production

Full implementation of the platform and integration with e-Services and evidence providers began in 2025. The OOTS platform is facilitating the provision of aggregate electronic services that allow companies and citizens to comprehensively resolve life situations electronically and is contributing to the connection between citizens and economic operators in the European economic area.