How do you submit a Dimona declaration for temporary workers while keeping your staff records accurate and up to date?

A new hire starts tomorrow morning. Is the Dimona already in? In Belgium, that single step decides whether an employment is legal from the very first hour. A Dimona declaration (immediate employment declaration) is the mandatory electronic notification an employer uses to register every employment with the National Social Security Office (NSSO). It forms the basis of Belgian social security and is essential for keeping your staff records accurate and up to date.

Permanent staff, occasional workers, student workers, temporary hires: whoever they are, every employer must submit a Dimona before the start time of the first working day. Get it wrong, or file it late, and you risk administrative fines and trouble during inspections.

This article walks you through the Dimona procedure from both angles, general and technical: how to work through the secure Dimona online service, which administrative instructions to follow, and how to stay compliant when details change or when an employee leaves the company. The result: your organisation stays fully in order with the social security institutions, and every new employment happens without stress or penalties.

What is Dimona, and why does it matter?

The name Dimona stands for Déclaration Immédiate, or immediate declaration. It's the digital system an employer uses to register every start and end of employment with the National Social Security Office (NSSO). Each electronic notification officially records the start and end time of an employment in the Dimona database.

Dimona has been mandatory since 2003 and applies to every employer in Belgium, whatever the sector. Hospitality, logistics, retail, non-profit: for every employee, the correct start date and end date go through the Dimona online service.

The big advantage? Dimona safeguards employees' social rights, makes inspections easier and helps prevent undeclared work. Your staff records stay accurate and up to date, fully in line with the social security institutions.

Who must file a Dimona, and who's responsible?

Every employer who hires someone must file a Dimona, whether the work is permanent, temporary or seasonal. For permanent staff, you file an electronic notification for each new employee before the start time of the first working day. The same applies to temporary workers, occasional workers and flexi-job workers in sectors like hospitality and retail.

Student workers count too, even for half a day of employment. For agency workers, the temp agency files the declaration, but you as the client stay responsible for checking that the data is correct and was sent on time.

Even replacement contracts, for illness, parental leave or holidays, need a registered Dimona. The employer is always the one ultimately accountable, so double-check that the declaration reached the NSSO correctly and matches your workers' actual employment.

When must you submit a Dimona?

A Dimona always has to be on time and correct. For every start of employment, you use a Dimona IN: declare the new employee before he or she actually starts.

When something changes, an extended contract, adjusted dates, a new role, you file a Dimona UPDATE straight away. That keeps your staff records current in the Dimona database.

When a contract ends, you file a Dimona OUT on the same day the employment ends. Forget it, and the NSSO keeps counting fictitious working days. The knock-on effects? Incorrect calculations, higher contributions, even administrative fines.

Filing a Dimona, step by step

Filing a Dimona follows a few fixed steps. First, log in to the NSSO portal (socialsecurity.be), or use a secure online service from your social secretariat or payroll software.

Next, pick the right contract type (student work, flexi-job, replacement, and so on). Most of the time a Dimona falls under the "Other" category, but in rare cases, such as occasional work in hospitality, you do need to select a specific Joint Committee (JC).

After that, enter the employee's national register number, or a BIS number for foreign workers without a Belgian one.

State the start date and end date, and for day contracts of flexi-job workers, the start and end time as well. For students, in that case, just the total number of hours worked that day. Then select the right status:

• STU for students
• FLX for flexi-job workers
• OTH for other temporary contracts

Finally, check every identification detail carefully and click "send". Save the receipt digitally as proof of a correct, on-time declaration.

Multi-Dimona option

The Multi-Dimona feature lives on the NSSO's official Dimona website. It lets you register several workers at once, as long as they share the same status. You choose the start and end date, add the working hours for day contracts, then enter a national register number for each worker.

There's a catch on the NSSO site: you can only register one type of worker per entry. Three flexi-job workers together, or two students, yes, but you cannot combine both categories in a single declaration.

Recruit makes this far smoother. You simply schedule your staff, whatever their status, and the system helps you generate the right Dimona declarations automatically. Students, flexi-job workers and other temporary staff, all managed in one workflow, without the limits of the classic Multi-Dimona.

Best practices for a flawless Dimona flow

A flawless Dimona flow starts with good preparation. Plan ahead and create the Dimona the day before your new employee starts. That way you know the start of employment is registered with the NSSO on time and social security is properly informed. Link your scheduling to your payroll system, and an automatic Dimona OUT notification follows the moment the end time or agreed period is reached.

Finally, archive every confirmation digitally in a secure system. The social security institutions can run checks going back up to five years, so a solid digital archive is indispensable.

Automating Dimona? Discover the power of Recruit

With Recruit, Dimona becomes a natural part of your HR processes. The platform completes every Dimona IN, UPDATE and OUT automatically, with no manual step from you. Every employment is registered flawlessly with the NSSO, fully in line with Belgian social security.

Recruit also applies the right sector salary scales, indexations and Joint Committees straight away, keeps every confirmation safe in the secure cloud, and gives you real-time dashboards of open contracts. It factors in student quotas, flexi-job conditions and any temporary unemployment too. So your staff records stay up to date, even in the busiest periods.

Conclusion: Dimona in a single click

A correct Dimona declaration is the foundation of watertight payroll. Respect the right status, the right Joint Committee and timely declarations, and you avoid NSSO fines while protecting your workers' rights, from before the employee even starts.

Ready to automate Dimona flawlessly? Discover how Recruit simplifies and optimises your declarations, and experience the power of a single click for complete, compliant and secure administration.