Limosa declaration in Belgium: the complete guide for foreign employers

If your company is established outside Belgium and you send employees to work there, even for a few days, you must file a Limosa declaration before they start. You file it online at limosa.be, you receive a LIMOSA-1 receipt immediately, and every posted worker must be able to produce that receipt to the Belgian client. Failing to declare is a level 4 offence under the Social Criminal Code, the heaviest category Belgium has. This guide covers who must declare, who is exempt, what else you need alongside Limosa, and what actually happens on a Belgian site.

What is the Limosa declaration?

Limosa is Belgium’s mandatory notification system for foreign workers. It tells the Belgian authorities that a worker employed by a foreign employer is going to work on Belgian territory, where, for whom, and for how long.

According to the Federal Public Service Employment, a foreign employer posting workers to Belgium, or their authorised representative, must inform the authorities through the website before the employment of those workers in Belgium begins.

Two points catch companies out repeatedly:

• It is prior notification, not a filing you catch up on. The declaration must exist before the work starts. There is no grace period.
• It applies from day one. There is no minimum number of days that lets you skip it, unless you fall inside one of the specific exemptions below.

For a construction company sending a crew of eight to a site near Antwerp for three weeks, that means eight declarations filed before the van leaves.

Who must file a Limosa declaration?

The obligation sits with the foreign employer, not the worker and not the Belgian client. You can delegate the filing to a payroll provider, a mobility consultancy or a legal representative, but the legal responsibility remains yours.

You must declare if you are:

• A company established outside Belgium posting employees to work in Belgium, whether on a construction site, in a factory, in an office or at a client’s premises.
• A temporary work agency established abroad supplying workers to a Belgian user.
• A self-employed person established abroad carrying out a temporary activity in Belgium, subject to the exemptions below.
• A foreign company sending a crew to install, commission or repair equipment you have supplied, beyond the short technical windows described in the exemptions.

The declaration is made each time a worker is sent to Belgium, and a single notification can cover an anticipated duration of up to 24 months. If the assignment runs longer than declared, you extend it.

What information do you need to file?

Have the following ready before you log in:

• Identification of the worker being posted.
• Identification of your company as the foreign employer, plus your liaison person. Belgium requires you to communicate the identity and contact details of a liaison person to the Belgian Labour Inspectorate, someone who can be reached about the posting.
• Identification of the Belgian client or principal the work is being carried out for.
• The place in Belgium where the work will be performed.
• The start and end date of the posting.
• The work schedule.

Once submitted, the system issues the LIMOSA-1 immediately. Print it, or make sure each worker has it on their phone. It is the document that gets asked for.

Who is exempt from Limosa?

A specific list of activities is exempt, and the thresholds are precise. According to Working in Belgium, the exempt categories include:

Read those limits carefully before relying on one. The 8-day assembly exemption in particular is narrower than most equipment suppliers assume, and it does not stretch to cover a project that overruns. If your installation slips to day nine, you needed a declaration.

We cover the edge cases and the common misreadings in more detail in our guide to Limosa exemptions.

Does an A1 certificate replace the Limosa declaration?

No, and this is the single most common misunderstanding.

• The A1 certificate proves which country’s social security system your worker remains affiliated to, so you do not pay contributions twice.
• The Limosa declaration notifies Belgium that the worker is physically working there.

They answer different questions and are issued by different bodies. Holding a valid A1 does not remove the Limosa obligation. You generally need both, and an inspector may ask for both. See our guide to A1 certificates in Belgium for what inspectors actually check.

Limosa, Dimona or Check-in-at-Work: which do you need?

Belgium has several registration systems and they stack rather than replace each other. In short:

• Limosa: you are a foreign employer posting workers to Belgium. Notification before work.
• Dimona: you are a Belgian employer declaring an employment relationship to the NSSO.
• Check-in-at-Work (CIAW): presence registration on qualifying sites, per worker, per day.

If you are a foreign contractor on a large Belgian construction site, you will often need Limosa and CIAW. Registration through Check-in-at-Work is mandatory for works on immovable property where the total value reaches 500,000 euro excluding VAT, and the registration must occur before the person begins work, daily, for each working day. Foreign employers need secure access to the Belgian social security portal and a Belgian company number (CBE) to do it.

The full comparison is in Limosa, Dimona or Check-in-at-Work.

One change worth planning for: a Programme Law adopted on 30 May 2026 extends mandatory registration to check in and out, covering works on immovable property above the same 500,000 euro threshold and the supply of ready-mixed concrete. It comes into force on 1 April 2027. If your systems only capture arrival today, you have until then to fix that.

What happens if you do not declare?

Non-compliance with Limosa is punished as a level 4 offence, the highest level in the Belgian Social Criminal Code. Level 4 carries the possibility of imprisonment alongside financial penalties.

The financial side got heavier recently. The Act of 19 December 2025 entered into force on 1 February 2026 and raised the multiplier applied to social criminal fines from 8 to 10, a 25 percent increase across the board. Published fine tables vary depending on whether they show the pre- or post-increase basis, so treat any single euro figure with care and take advice on your own exposure. What is not in doubt is the structure: level 4 is the heaviest category, and for some infringements the amount is multiplied by the number of workers involved, up to a maximum of 100.

That last clause is what turns a paperwork slip into a serious number. A single missed declaration is a problem. Twelve undeclared workers on one site is a different order of magnitude.

Beyond the fine, an inspection that finds undeclared workers can stop the work. On a site with liquidated damages running, the delay usually costs more than the penalty.

Why your Belgian client will ask for your paperwork

Belgian clients and main contractors are not being difficult when they chase you for a LIMOSA-1. They are managing their own exposure.

• Reporting duty. If a posted worker cannot produce the LIMOSA-1, the Belgian principal or client has to report this to the Belgian government.
• Joint and several liability. In construction-related activities, the client who engages a contractor is jointly and severally liable for paying the wages due to that contractor’s workers. In a subcontracting chain, a party notified in writing by the Inspectorate that a subcontractor further down the chain has seriously failed to pay wages becomes liable for those wages.
• Withholding obligation. If a contractor has outstanding social or tax debts, the client must withhold part of each invoice and pay it to the authorities directly: 35 percent of the amount excluding VAT for social security debts to the NSSO, and 15 percent for tax debts to FPS Finance. Since 1 May 2026, a further 15 percent applies for outstanding self-employed social contributions. Clients check this at checkinhoudingsplicht.be.

Read together, these rules mean your compliance is your client’s financial problem. The contractors that get invited back are the ones who make this easy: declaration filed early, LIMOSA-1 available on request, presence registration working from day one.

How to get this right operationally

The legal requirements are clear enough. What goes wrong is operational: the declaration filed on the morning of day one, the worker who swapped onto the crew without anyone updating the notification, the site where nobody can prove who was present last Tuesday.

A few practices that hold up under inspection:

• File at the point the crew is confirmed, not at mobilisation. Late changes are easier to amend than to create.
• Keep the LIMOSA-1 with the worker, not in an office in another country.
• Treat crew changes as a compliance event. A substitution on Friday afternoon is a new declaration, not an informal swap.
• Register presence digitally. Paper sign-in sheets do not survive an inspection well, and they cannot produce a per-day record retroactively. A digital check-in-at-work flow, tied to the worker and the site, gives you a defensible record without adding a job for the foreman.
• Name a real liaison person who answers their phone. The requirement is not a formality.

Compliance should be simple and digital. If your Belgian obligations depend on someone remembering to do something at 6:45 on a wet Monday morning, they will eventually not be met. Our workforce management platform is built so registration happens as a by-product of people arriving at work, rather than as an extra administrative task.

For a worked example, see how Cegelec handles presence registration across multiple Belgian sites.

If you are looking for the guide that matches your own country of establishment, start from the full compliance overview for foreign employers.

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