What is a Dimona Declaration in Belgium?

What is a Dimona declaration?

Dimona (Déclaration IMmédiate / ONmiddellijke Aangifte, the immediate declaration of employment) is the electronic notice an employer in Belgium sends to the National Social Security Office (NSSO, also known as ONSS or RSZ) each time an employee starts or stops working. It puts the employment on record with Belgian social security.

When to file Dimona IN and Dimona OUT

A Dimona IN must reach the NSSO at the latest when the employee actually starts work. It can be filed earlier, for example in the previous month, and it records the legal or contractual start date, which can differ from the first day worked.

A Dimona OUT is due at the latest on the first working day after the employment ends. When dates change, the employer files a modification or, where the rules require it, cancels the period and declares a new one.

Who has to file

Every employer with staff under Belgian social security files Dimona, whether the employer is based in Belgium or abroad. Some groups follow their own rules. Students are declared with the worker type STU no later than the day they work, and occasional workers in sectors such as hospitality and horticulture have a declaration that records their working hours.

Why it matters

Dimona has applied to all employers since January 2003. It feeds the Crossroads Bank for Social Security, which the authorities use to spot undeclared work, and it is how an employee’s social rights are recorded. A late or incorrect declaration can delay the employee’s holiday pay or family and maternity benefits, and failing to file is an offence under the Social Penal Code.

Dimona when you hire through an EOR

When you hire through TopSource as your Employer of Record in Belgium, we file the Dimona IN with the NSSO before your employee’s first day and the Dimona OUT when the employment ends. As the legal employer, we also keep the record up to date if dates or hours change.

Frequently asked questions

When must a Dimona be filed?

A Dimona IN is due at the latest when the employee starts work, and a Dimona OUT at the latest on the first working day after the employment ends.

Does a foreign company employing someone in Belgium need to file Dimona?

Yes, if the employee is covered by Belgian social security. A company without a Belgian entity can hire through an Employer of Record instead, which registers as the employer and files the declarations itself.

What happens if an employer does not file Dimona?

The work is treated as undeclared. The employee’s social security rights can be delayed, and the employer faces penalties under the Social Penal Code.

Dimona Declaration (Belgium)