32px_Search Created with Sketch.
Shape Created with Sketch. Back to projects

Once Only

According to the Once Only principle, administrations may no longer ask users (citizens and businesses) to provide information these administrations already have access to through data from authoritative sources (e.g. household composition, tax assessment notice, social insurance certificate, etc.).

The Brussels Capital Region has decided to make all Brussels administrations apply the Once Only principle as of 2021 and bring the existing procedures into compliance (forms).

Click here to inform us of a procedure that doesn’t comply with the “Once Only” principle

You are a Brussels public administration


The Once Only principle in the Brussels Capital Region (regulatory framework)

Previously, several regulations governed the Once Only principle. However, all of these regulations were applicable on condition that the public administrations/services had access to the authoritative sources. Consequently, they were not applicable if the administrations had not asked for access to these sources.

Since the ordinance dated 17 July 2020 , Brussels administrations and services must apply the Once Only principle.

Obligations in the framework of the ordinance dated 17 July 2020

What are the new obligations for Brussels administrations as of 2021?

  • Obligation to request an identification key in all administrative forms: the national register number, the Crossroads Bank for Social Security identification number or the business number;
  • Prohibition on asking citizens/businesses for information that is accessible in the authoritative sources;
  • Obligation to use the authoritative sources: consult the list of authoritative sources that are available in Belgium.

The forms

The ordinance also specifies that electronic forms and their attachments are reputed to have the same value as paper forms, provided that the following conditions are met:

  • For existing forms: an identification key must be requested in the form. Should this not be the case yet, the public authorities have until 1 January 2021 to bring the forms into compliance.
  • For new forms: these must be submitted to easy.brussels at least 45 calendar days before they are first used.

Ensuring compliance

Before undertaking any compliance steps, consult the “Once Only Decision Tree”, also attached, so as to take the right steps for your situation.

Once Only Decision Tree

Click on the picture. It will be displayed in a new tab, which will allow you to consult (via a zoom) all the compliance steps.

Once Only - Decision Tree easy.brussels - November 2020

Once Only – Decision Tree easy.brussels – November 2020

You are a user (citizen, company, etc.)


The Once Only principle in the Brussels-Capital Region and the authentic sources

Authentic sources thus first and foremost meet the needs of users. As a result, citizens and businesses no longer have to provide information they have already shared with an administration. Users only have to provide information once and it is then collected and shared within the administrations. This is the Only Once principle of data collection.

Another undeniable advantage is that using the authoritative sources ensures that the collected data are safe and practical. The advantage of authentic sources for administrations lies in the fact that they are safe and practical. They allow administrations to make life easier for users, become more flexible and operate better and more autonomously, without disturbing users. This means that they reduce the administrative burdens on citizens and businesses, avoiding unnecessary expense and travel that can impact their schedule.

Use of your data / Protection of your privacy

The subject of authentic sources leads to questions about respect for privacy, which is why their use involves strict safety and confidentiality conditions.

To be recognised as an authentic source and guarantee effective information management, a database must:

  • be validated by one or more administrations;
  • be regularly updated by one or more administrations;
  • be legitimated by at least one administration that acts as the unique authentic source manager;
  • only be accessible in a secured and controlled way.

The most frequently used authentic sources at federal level are:

  • the national Register, which includes personal information about Belgian and foreign citizens living in Belgium.
  • the Crossroads Bank for Enterprises (CBE), which centralises the key data on legal persons, businesses and units of establishment.

In the Brussels-Capital Region, the Fidus platform, managed by the BRIC (The Brussels Regional Informatics Centre) is the legal manager of data exchanges from authentic sources. These exchanges can be between Brussels and federal institutions, as well as at intra-regional level.

easy.brussels is encouraging Brussels institutions to use authentic sources at both regional and local levels thanks to the advantages they offer for administrative simplification. To do so, the agency is working closely with the BRIC to raise awareness among the administrations.

You wish to inform us of a procedure that could be simplified?

In the context of its missions, easy.brussels makes sure that the Once Only principle is implemented in the Brussels-Capital Region. According to this principle, administrations can no longer ask you for information that can already access (for example: household composition, fiscal documents, social certificate, etc.).

You can inform us of any administrative procedure related to a public administration of Brussels (regional, local, public association, etc.) that doesn’t comply with the Once Only principle or that could be simplified. To do so, please fill in the following form:


Once Only signalement EN
You are: *