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    Steps to Take at the NSSO

    When hiring one or several workers for the first time, you need to undertake the following steps:

    • Register yourself as an employer with the NSSO
    • Submit an immediate employment declaration (DIMONA)
    • Complete a quarterly multifunctional declaration

    Identifying Yourself as an Employer with the NSSO

    Identification with the National Social Security Office (NSSO) can be done via the Wide online service accessible on the portal site of the Social Security.

    Making a "DIMONA" Declaration

    Once you hire staff, it is imperative to submit an immediate employment declaration (DIMONA) to the NSSO.

    The process is mandatory for all employers in all sectors of activity and can only be done electronically.

    With the declaration you inform the NSSO that you employed someone within the company.

    Each employee is assigned a personalised DIMONA code which allows the social security bodies to immediately know the information relating to the identity and the employer-employee employment relationship and any changes to it, such as employee departures. As such, the information needs to be provided only once.

    Wide is directly integrated into the DIMONA online service, enabling any new employer to declare their first employee when identifying themselves to the NSSO.

    Making a Quarterly Multifunctional Declaration

    In addition, you have to submit a quarterly multifunctional declaration to the NSSO, which states the work and remunerations of all your employees.

    How Much Do These Steps Cost?

    These formalities are free of charge, if you complete them yourself.

    A fee is charged, if a business counter or a social secretariat is involved. Other intermediaries can also assist you in these steps, for a fee (specialised offices, employers' organisations, etc.).

    More Information

    All useful information and forms are available on the portal site of the social security. The NSSO website "" also offers a concrete overview of all the information you need as a future employer.

    National Social Security Office (NSSO)
    Place Victor Horta 11
    1060 Brussels
    Tel.: +32 2 509 59 59
    Website of the NSSO -
    Instructions administratives

    Affiliation to a Certified Social Secretariat or a Social Service Provider

    An employer can use a certified social secretariat or a social service provider to have his/her social obligations fulfilled, including those towards the National Social Security Office (NSSO).

    Social service providers and social secretariats are representatives of the employer who deal with the administrative formalities towards the social security institutions on behalf of the employer. They must also provide the employer with the necessary information to fulfil his/her obligations.

    Certified social service providers and social secretariats are all private service providers. Their services are paid for by the employer-customer. 

    What Is the Difference Between a Certified Social Secretariat and a Social Service Provider?

    The difference between these two categories of intermediaries is that certified social secretariats are bodies recognised and controlled by public authorities. Only certified social secretariats can collect social contributions from affiliated employers and then pay them to the institutions responsible for collecting social security contributions (mainly the NSSO). The NSSO must be informed of this mandate by means of a document ("proxy").

    Often, business counters have a related social secretariat which they will suggest you use.

    The list of certified social secretariats is available on the website of the Union of Social Secretariats.

    Costs of Affiliation to a Certified Social Secretariat

    As a new employer, you can benefit, under certain circumstances, from a financial contribution of the NSSO to help cover the costs resulting from your affiliation to a certified social secretariat.

    This contribution may be granted to you in the following scenarios:

    • When you hire your first employee (and up to a maximum of six employees), and provided you have received the reduction in employer's social security contributions for “first employment” when hiring this worker;
    • If your business operates in the hospitality sector.

    Other Administrative Formalities

    In addition to the steps with the NSSO and the possible affiliation to a certified social secretariat, you will also have to fulfil various other obligations:

    • Affiliation to a family allowance fund;
    • Taking out insurance against accidents at work;
    • Compliance with legislation on well-being at work;
    • Compliance with the conditions of employment of workers, etc.

    Withholding Tax

    Any business owner, whether self-employed or a company, who wishes to hire staff must meet various tax obligations.

    A self-employed person or a company that pays or grants remuneration, including benefits of any kind such as company cars, computers, mobile phones, housing, etc., to their employees or workers must deduct withholding tax. You are entitled to deduct this withholding tax from the taxable income you pay or allocate.

    If you bear the withholding tax that is due yourself instead of deducting it, this constitutes a benefit in kind that is taxable on the part of your employees.

    The withholding tax is calculated on taxable remuneration after deduction of personal social security contributions.

    You are also responsible for electronically submitting the withholding tax declaration within 15 days after the end of the month or quarter in which you paid or allocated the remuneration.

    The withholding tax due must also be paid in full within the same period, unless an exemption from payment can be applied to you. In the latter case, you are fully or partially exempt from paying the withholding tax that is due to the Treasury.

    There are various exemptions from paying withholding tax. These apply to the following:

    • Additional work;
    • Researchers;
    • Shift work and night work;
    • Shift work and real estate work;
    • Wage adjustment (AIP);
    • Investments in an assisted zone;
    • Start-up companies;
    • Young employees;
    • Employee training;

    The conditions and rules for exemption vary for each of those cases.

    In order to corroborate the declarations made, you must electronically file tax slips on behalf of each income recipient before 1 March of the year following the year to which the slips relate.

    You will find more information about the withholding tax on professional income in the "Staff and remuneration" section on the website of the FPS Finance. 

    Last update
    19 April 2024