Page tree

Once Only Principle

Reduce administrative burden for individuals and businesses

What is the Once Only Principle?

The Once Only Principle entails that citizens and businesses provide diverse data only once in contact with public administrations, while public administration bodies take actions to internally share and reuse these data – even across borders – always in respect of data protection regulations and other constraints. The Connecting Europe Facility’s digital programme supports the application of this principle.

OOP and CEF: Currently, the Once Only Principle (OOP) is undergoing a preparatory action within CEF. The various work packages will define if this should be considered as a Building Block or as a service of an existing Building Block.

"Businesses should also be able to set up more quickly and expand across the European Union. We want to help them do this by extending the 'once-only' principle for businesses to operate across EU borders."

Vice-President Andrus Ansip: Setting the scene for a Digital Single Market

What is the Policy Context?

At the European level, the Once Only Principle has for the first time been mandated by the  inclusion in the Single Digital Gateway Regulation. By 2023, citizens and businesses can request that an evidence for something asked for by an administration as part of an online procedure is exchanged directly between the administration requesting it and the administration holding the evidence in another Member States. This makes the most common procedures, such as changing an address, much easier and less burdensome. Two EU initiatives work directly towards setting up the ‘once-only’ infrastructure that will enable the once only exchange under the Single Digital Gateway:

  • TOOP: The Once-Only Principle Project (TOOP) was launched by the European Commission in January 2017 as an initiative of about 51 organisations from 21 EU Member States and Associated Countries. The main objective of TOOP is to explore and demonstrate the once-only principle across borders, focusing on data from businesses. Doing this, TOOP wants to enable better exchange of business related data or documents with and between public administrations and reduce administrative burden for both businesses and public administrations;
  • SCOOP4C: was launched in November 2016 and it is funded under the H2020 call CO-CREATION-05-2015. Five organisations from four different member states explore how the once-only principle for citizens can be implemented.

A range of European initiatives supporting cross-border digital public service provision such as the eGovernment Action Plan 2016-2020 and the Tallinn Declaration on eGovernment.

The Once Only Principle will be applied in accordance with rules on data protection and privacy. The GDPR has raised the bar for the protection of personal data in Europe, including with respect to transparency and the requirements for a legally valid consent. The application of this principle therefore needs to be in compliance with the EU data protection legislation, as is the case for the once only infrastructure developed to support the Single Digital Gateway.

What's in it for me?

Any digital public service applying the Once Only Principle essentially revolves around re-using data held by one administration by providing it directly to another. This is hugely beneficial for the end user. It's easy, reduces time and effort, and decreases the chance of mistakes since existing trustworthy data doesn’t have to be manually re-used repeatedly.

The principle is applied to a number of other policy domains to reduce the administrative burden for citizens and business, including but not limited to the exchange of company data in public procurement, in the domain of customs and VAT, student exchange and the maritime sector. These initiatives  will serve to support and complete the Digital Single Market. The infrastructure that will be set up under the Single Digital Gateway Regulation may also have the potential to enable the application of the once only principle across a number of EU policy domains.

Key Date


Deadline to comply with the European standard on Once Only Principle


Download our flyer

Learn more about Once Only Principle

For more information, see also:

Building block reuse

Once Only Principle has committed to reuse the eDeliveryeID and eSignature building blocks.


Exchange data and documents securely and reliably.


Offer digital services capable of electronically identifying users from all across Europe.


Create and verify electronic signatures in line with European standards.