Declaring employees

An employer must declare its employees to the NSSO. Which employees? And which declarations must be submitted?

Which employees must be declared?

The vast majority of employees in Belgium work under a traditional employment contract and therefore must be declared to the NSSO. But sometimes the situation is less clear.

Employees to be declared

Persons with an employment contract

The most important group of employees to be declared are persons with an employment contract. With such a contract, an employee undertakes to perform paid work under the authority of his or her employer. This employer may belong to the private or public sector.

The ‘legal presumption’ of an employment contract exists for some groups: the law assumes that these employees have concluded an employment contract. They therefore must be declared – unless it can be demonstrated that no employment contract was concluded. Pharmacists and sales representatives among others belong to the professions covered by this scheme.

More information can be found in the Administrative Instructions. (*)

Similar conditions

Persons who work under ‘similar conditions’ to those of an employment contract must be declared. A person works under similar conditions when his or her work corresponds with a legal definition. Hence it is not necessary that work is performed in a relationship of subordination. Similar conditions exist among others for freight carriers and childminders.

More information can be found in the Administrative Instructions. (*)

Student workers

Student workers (*) pay only a ‘solidarity contribution’. Yet they must be declared with the NSSO.


For the NSSO, apprentices (*) are ordinary employees and must therefore be declared.

Statutory public sector personnel

The declaration obligation also applies to statutory public service personnel, regardless of the entity to which the government agency belongs, whether federal, regional, local or provincial.

Employees who do not have to be declared

Some people perform work of a limited scope and therefore are not covered by social security for employees. If the necessary conditions are met, this is the case for volunteers, artists with a specific small fee and some workers in the socio-cultural sector.

More information can be found in the Administrative Instructions. (*)

What rules apply to cross-border employment?

The obligation to declare and other Belgian social security rules apply not only to Belgians working in Belgium. They may also be applicable to employees of other nationalities and to employees who work abroad and are employed by an employer based in Belgium.

Which rules apply – Belgian or foreign – is usually determined by an international treaty or the domestic legislation of Belgium or another country.

At a glance

  • For employees working in the EU, the EEA (European Economic Area) and Switzerland, the EU rules apply.
  • For employees working in Belgium or a country with which Belgium has concluded a bilateral treaty, the rules of that treaty apply.
  • For employees working in Belgium or a country with which Belgium has not concluded a bilateral treaty, the general principles of cross-border employment apply.

Employees in the EU

For employees in the EU, the EEA and Switzerland who practice their profession in any of these countries, the EU rules on social security apply.

The applicable legislation guide of the European Commission gives an overview of the rules.

Bilateral treaties

Belgium has concluded a social security agreement with many countries outside the EU, the EEA and Switzerland (*)(such as Morocco and the US). Some of these agreements apply only to nationals of the countries that have signed the agreement, others also apply to nationals of other countries.

The main principles of the bilateral agreements are the following:

Situation of the employee Principle
The employee works in the territory of a single country The rules of the country of employment apply
The employee works temporarily in another country (secondment) Employees who are sent abroad by their employer for a temporary assignment in principle remain temporarily insured under the Belgian social security scheme for employees. The employer must continue to pay contributions to the NSSO.
The employee works in the territory of both countries The employee is subject to the rules of each country for the activities carried out there. Each employer must fulfil its obligations towards the social security institutions of each country where it employs employees.

No bilateral treaty

If no treaty is applicable, then the general rules for cross-border employment apply. There are two basic scenarios: employees who come to work in Belgium and employees who go to work abroad.

Coming to work in Belgium

For employees of an employer established abroad who come to work in Belgium, the decisive factor is whether the employee does or does not depend on a Belgian place of business.

If the employee depends on a place of business... then ...
in Belgium the Belgian rules apply. Each employer must fulfil its obligations towards the social security institutions of each country where it employs employees.
abroad the Belgian rules do not apply.

Going to work abroad

For employees who go to work in a country with which Belgium has no treaty, the intended duration of employment is decisive.

If the expected duration of employment is ... then ...
less than six months the Belgian rules apply (if the employee is not registered with the Overseas Social Security of DIBISS)
more than six months the employee is not subject to the Belgium rules. He or she may register with the Overseas Social Security of DIBISS.

In addition to the Belgian rules, the rules of the other country can also apply.

Determining applicable social security scheme

It is often difficult to determine the applicable social security scheme for someone who goes to work in another country. There are two applications on the social security portal that can help.

Both applications use search criteria to provide a brief description of the social rights and obligations in a given situation. You can also find information there on the departments to which you can address your questions.

More information

The brochure "Everything you always wanted to know about social security" of the FPS Social Security provides an overview of the international aspects of social security.

Lists can be found of social security organisations throughout the world on the website of the FPS Social Security (*) and the American Social Security Administration.

What declarations must the employer submit?

An employer must submit the Dimona and DmfA declarations to the NSSO. In practice, many employers outsource these declarations to a social secretariat or payroll services firm.


In the Dimona declaration, an employer informs the government of its active working relationships. The employer must make a Dimona declaration whenever:

  • it hires someone, before this employee starts to work;
  • an employee leaves employment, no later than the next business day after the resignation or departure of the employee.

These declarations must be made electronically.

More information

All details about Dimona can be found on the social security portal:


The DmfA (the multifunctional declaration) is a quarterly declaration on the work performed by and salaries of employees.


The main goals of the DmfA are:

  • determining the amount of social security contributions employers and employees must pay;
  • the one-off communication to the government of the salary and work information of all employees. As a result, if a worker must appeal to social security, much information about him or her is already available that the benefit agencies need not request again.

The DmfA must also be made electronically. This makes it possible to make the data available in the network very quickly.

More information


(*) If not available in English, the page will show in another language. Most pages are mainly available in Dutch and French, sometimes in German.
The Administrative instructions and the online applications on the Social Security Portal are only available in Dutch or French.

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