Belgian rules on the posting of workers are among the most strictly enforced in Europe. For companies installing sandwich panels on Belgian construction sites, Limosa is not optional — it is a legal obligation, and failing to comply results in an immediate work stoppage and fines calculated per worker.
What Limosa Is and Who It Applies To
Limosa (Landenoverschrijdend Informatiesysteem ten behoeve van Migratieonderzoek bij de Sociale Administratie) is Belgium's electronic declaration system for posted workers, mandatory since 1 April 2007. Every employee or self-employed person who temporarily carries out work in Belgium and is not covered by the Belgian social security system must be registered before their first working day.
The obligation applies to companies from Poland, the Netherlands, Germany, and any other EU member state posting workers to Belgian construction sites.
Who Submits the Declaration
A Limosa declaration can be submitted by:
- an employer based outside Belgium (the most common scenario in subcontracting),
- a self-employed worker,
- a temporary employment agency.
In practice: if a Polish company is installing Kingspan or Ruukki panels at a Belgian industrial facility, it is the Polish company that files the Limosa declaration — not the Belgian main contractor. The main contractor is required to verify that the declaration has been filed, but the responsibility for filing it lies with the subcontractor.
How to File a Limosa Declaration — Step by Step
Registering in the System
Before submitting the first declaration, the company registers on the limosa.be platform. Information required:
- the company's VAT number,
- registered address,
- details of the person authorised to submit declarations.
Registration is a one-time process. Subsequent declarations are filed from the same account without re-verifying the company.
Information Required for Each Declaration
Each declaration must include:
- worker details: first name, surname, national identification number or identity document number, nationality,
- the posting period (start date — end date),
- the exact address of the construction site,
- the type of work being performed (NACE code),
- details of the Belgian client or main contractor.
For construction work, the NACE code is most commonly 43.99 (other specialised construction activities) or 41.20 (construction of residential and non-residential buildings). It is worth confirming the correct code with the Belgian client before filing — misclassification often triggers questions during inspections.
The Limosa-1 Document
Once the declaration has been filed, the system generates a Limosa-1 document. This certificate:
- must be accessible to every worker on the construction site,
- can be requested by a Belgian labour inspector at any time,
- expires at the end of the declared period.
Paper and electronic formats are equally valid. A PDF on a mobile phone is accepted by SIOD inspectors.
Deadlines, Penalties and Common Mistakes
When to File the Declaration
The declaration must be filed before the worker's first day on Belgian soil. Not on the day of arrival, not by the end of the week — before. For planned works, filing 2–3 working days in advance is recommended to allow a buffer for any technical issues with the platform.
The regulations do provide for an emergency procedure covering urgent interventions (for example, repair of roof cladding following mechanical damage), but this is an exception that requires documented evidence of urgency — it is not a substitute for poor planning.
Penalties for Non-Compliance
The Belgian Labour Inspectorate (SIOD/GDSI) carries out regular site inspections, particularly on large industrial and logistics projects. The applicable fine ranges are:
- failure to file a Limosa declaration: from €500 to €4,000 per worker,
- work performed outside the declared period: the same fine range applies,
- worker on site without a Limosa-1 document: from €250 to €2,500.
Repeated violations can result in the company being placed on Belgium's blacklist of construction subcontractors, which in practice closes the door to contracts with major main contractors in that market.
Common Mistakes
The most common mistake: filing a declaration for too short a period. Works run over, the worker remains on site beyond the date entered in Limosa — and inspectors treat this identically to having no declaration at all.
The fix is straightforward: always declare with a 1–2 week buffer beyond the planned completion date. Updating the date in the system is free and takes a few minutes, and it eliminates the risk entirely.
The second mistake: one entry covering an entire crew. Every worker must be declared individually, with their own identification number. Collective declarations do not exist in the system and are not accepted.
The third mistake: failing to update the declaration when changing sites. A declaration is tied to a specific location. Moving a worker to a different site in Belgium — even in the same week, under the same framework contract — requires a new or updated declaration.
Limosa and Other Belgian Requirements
Limosa is the starting point, not the complete checklist. Belgian legislation on posted workers also covers:
- A1/E101 Certificate: confirms that the worker remains subject to the social security system of the sending country. Issued by the relevant national authority. Without this document, Belgian authorities may challenge where social contributions are being paid.
- Belgian minimum wage rates (PC 124): the sectoral collective agreement for the construction industry. Posted workers are entitled to Belgian minimum rates where these are higher than the home country rates. In practice, for skilled installers, the differences can be significant.
- Construction Identification System (CIS): registration required for construction companies exceeding a defined threshold of revenue from works carried out in Belgium.
- Document retention: the Belgian employer or their appointed liaison officer is required to retain specified documents for the duration of the works and make them available to inspectors on request.
The main contractor in Belgium will typically provide their own compliance document checklist. It is worth reading carefully — internal procedures vary between companies, but Limosa and the A1 certificate are always on the list.
The key practical takeaway: file the Limosa declaration before the crew leaves for Belgium, not on the day of installation. File individually for each worker, with a time buffer and the address of the specific site. The Limosa-1 document must be physically accessible on site — not in the office, not with the project manager back home. Companies that treat this requirement as a standard part of job preparation do not have problems with Belgian inspectors. Companies that leave it to the last minute pay fines many times higher than the cost of getting the paperwork right.