Status on 22 October 2026: the sanction amounts below apply to offences from 1 February 2026. Check In and Out at Work replaces Checkinatwork on construction sites from 1 April 2027.
Limosa is the mandatory online declaration to the Belgian social security authorities before work starts in Belgium.
It applies when a non-Belgian employer posts workers to Belgium, and when a self-employed person from abroad comes to work in construction, meat or cleaning.
The declaration gives you an L1 certificate. On a large Belgian construction site, that L1 is also how each foreign worker checks in every day.
We build the Check in at Work solution that Belgian contractors use on those sites. This guide covers:
- The flow from Limosa declaration to site check-in, with who does what
- Who must file, and who is exempt
- What a missing declaration costs
- How Limosa differs from an A1 certificate
- What changes on 1 April 2027
Limosa in one flow: from declaration to site check-in
The government explains each step on a separate page. On site, the steps form one chain, and the chain is where it goes wrong.
- Before work starts: the declaration. The foreign employer files it with the RSZ/ONSS for employees. A self-employed person files with the RSVZ/INASTI.
- The receipt: the L1 certificate. The declarant receives a PDF, the L1. The worker must be able to show it to inspectors.
- The QR code. Since 1 March 2014, the L1 carries a QR code that links to ‘Check Limosa’.
- The Belgian client checks. Every client or user in Belgium, directly or through subcontracting, checks that each posted person has an L1.
- Missing L1: report it. The client reports anyone without an L1 electronically, before that person starts work.
- Daily site check-in. On a Checkinatwork site of EUR 500,000 excl. VAT or more, each foreign worker is registered every day before starting, by scanning the L1 QR code. The L1 number is their ID.
| Who | What they do | When |
|---|---|---|
| Foreign employer | Files the Limosa declaration and passes the L1 to each worker | Before work starts |
| Self-employed person from abroad (construction, meat, cleaning) | Files their own declaration | Before work starts |
| Worker | Carries the L1 and shows it to inspectors | Every day in Belgium |
| Belgian client or main contractor | Checks each L1 and reports anyone without one | Before work starts |
| Site manager | Makes sure each foreign worker is registered by scanning the L1 | Every day, before work |
Tip: the RSZ says a foreign worker can scan the L1 QR code without secure access to the Belgian social security portal. A foreign contractor can scan its crew’s L1s the same way, according to the RSZ page on who Checkinatwork is for.
The Check in at Work rules for each activity explain when a site is in scope and who registers in the chain.
Who must file a Limosa declaration?
Two groups must declare before they start work in Belgium.
| Group | Condition | Files with |
|---|---|---|
| Employees | Normally work abroad or were hired abroad, and are posted temporarily or partly to Belgium by a non-Belgian employer | RSZ/ONSS, by the employer |
| Self-employed people | Not established in Belgium, and come to work in construction, meat or cleaning | RSVZ/INASTI, by the self-employed person |
That covers employers from the Netherlands and other EU countries as much as from outside the EU. What counts is that the employer is not Belgian.
You file the declaration online at limosa.be. No source we checked gives a deadline in hours or days: the rule is before work starts.
Posting also brings other duties, such as Belgian minimum pay and the sector’s conditions, a contact person and keeping social documents. This guide does not cover those.
Which short assignments are exempt?
Some short assignments are exempt. The exemption depends on the activity and on how long it lasts.
| Activity | Limit |
|---|---|
| International transport | Exempt, but not cabotage |
| Scientific congresses | Exempt |
| Meetings in a closed circle | Max 20 consecutive days and 60 days a year |
| Installation or assembly of supplied goods by specialised staff | Max 8 days, and never for construction work |
| Urgent repair of machines | Max 5 days a month |
| Sport events | Exempt |
| Renowned artists | Max 21 days a quarter |
| Researchers | Max 3 months a year |
| Diplomats and civil servants | Exempt |
| Self-employed business people or company directors | Max 5 days a month |
The limits come from the RSZ’s list of exemptions.
Note: the 8-day installation exemption does not apply to construction work. A crew that builds or renovates in Belgium declares, however short the job.
The edge cases are in our article on Limosa exemptions.
What a missing declaration costs: a worked example
The Social Penal Code sets the sanction level by who failed, and multiplies the fine by the number of workers.
| Who failed | Level | Administrative fine | Criminal fine |
|---|---|---|---|
| Employer with no declaration | 4 | EUR 3,000 to 35,000 | EUR 6,000 to 70,000 |
| Self-employed person with no declaration | 3 | EUR 1,000 to 10,000 | EUR 2,000 to 20,000 |
| Client who did not report a missing L1 | 3 | EUR 1,000 to 10,000 | EUR 2,000 to 20,000 |
These amounts apply to offences from 1 February 2026; earlier offences use the old, lower amounts.
Take a foreign contractor that sends four workers to a Belgian site without a declaration. At level 4, the administrative fine runs from EUR 12,000 to 140,000.
If the Belgian main contractor did not report the missing L1s, it faces its own level 3 fine, times four.
On a Checkinatwork site, a missed daily registration is a separate level 3 sanction per person involved.
That is why Belgian main contractors check foreign subcontractors before work starts. Our guide on liability for foreign subcontractors explains what they look at.
Is an A1 certificate enough?
An A1 certificate shows which country’s social security covers the worker. The Limosa declaration tells Belgium that the person is working on its territory.
They answer different questions, so an A1 does not replace Limosa. A Dutch employer gets the A1 from the SVB; our guide on the A1 from the SVB walks through it.
Checkinatwork is a third step again: it records who is present on a site each day. The differences between Limosa, Dimona and Checkinatwork are set out side by side.
What changes on 1 April 2027?
From 1 April 2027, Check In and Out at Work replaces Checkinatwork for construction and ready-mix concrete.
Each person on a site of EUR 500,000 or more then checks in and checks out in real time.
The legal basis is the Programme Law of 30 May 2026, articles 124 to 131. The Limosa declaration itself stays the step before the site.
If your crews only register on arrival today, plan for the check-out now.
Frequently asked questions
Is Limosa mandatory?
Yes, for the two groups above, unless an exemption applies.
What is a Limosa certificate?
It is the L1, the PDF receipt of the declaration. The worker must be able to show it to inspectors.
How do you apply for a Limosa declaration?
Online, before work starts. Employers declare employees with the RSZ/ONSS; self-employed people declare with the RSVZ/INASTI.
Who checks the L1 on a Belgian site?
The Belgian client or user, directly or through the subcontracting chain. They report anyone without an L1 before work begins.
Make the L1 part of your site check-in
For Limosa and Checkinatwork, three things must line up every day: a Limosa declaration, an L1 in each worker’s hand, and a site registration made before work.
Before the crew leaves for Belgium:
- File a declaration for each worker who is not exempt.
- Send each worker their L1, so they can show it on site.
- Send the L1s to your Belgian client, who has to check them.
- Ask the main contractor how the site registers people: poster QR code, app or site pole.
- Treat a crew change as a new declaration. A replacement worker needs their own L1 before starting.
When the check-in runs on the L1, the L1 number is each worker’s ID in the site record, so you can match it to the declarations.
Book a free demo and we will show you how Check in at Work runs on a site with foreign crews.
