The Netherlands is the second-largest source of posted workers into Belgium, and Dutch companies are the single biggest group in the petrochemical, electrical installation and metalworks sectors. Proximity makes it feel routine. It is not: a Dutch employer sending a fitter to Antwerp for two days has the same Limosa obligation as a company flying a crew in from the other side of Europe.
Where Netherlands sits in the Belgian market
Dutch companies filed for 43,505 posted persons into Belgium in 2023, 18.8 percent of the Limosa total. The profile is distinctive: the Netherlands is the top country of establishment for posting companies in the petrochemical industry (47 percent), electrical installation and assembly (24 percent) and metalworks and pipefitting (20 percent), and supplies 15 percent of construction posting companies. Dutch nationals are also the most common nationality among posted workers in the Belgian petrochemical, transport and cleaning sectors.
One trend worth knowing: the Dutch figure has been falling, from around 53,300 in 2021. Much of that decline is a data artefact rather than a real drop, because road transport postings moved to the EU portal and no longer appear in Limosa at all. If you post drivers, do not assume the Limosa question has gone away for your other activities.
The four things you must have
Work backwards from your mobilisation date, because two of these depend on third parties.
1. A1 certificates, applied for at the Sociale Verzekeringsbank (SVB) before departure, one per posted worker, covering the full planned period. They prove your people stay in the Dutch social security system rather than becoming liable for Belgian contributions. See what Belgian inspectors check on an A1. 2. A Belgian company number (CBE) and portal access, if Check-in-at-Work will apply. Foreign employers need both to register presence at all, and this is the step most often left too late. 3. The Limosa declaration, filed at limosa.be before the first day of work. It produces a LIMOSA-1 receipt each worker must be able to show to the Belgian client. Full detail in our Limosa guide. 4. A liaison person, whose identity and contact details you give to the Belgian Labour Inspectorate, and who can actually be reached about the posting.
Does the A1 replace the Limosa declaration?
No, and this is the most expensive misunderstanding in cross-border work.
The A1 answers which country’s social security system applies. Limosa answers whether Belgium knows your worker is on its territory. They are issued by different bodies for different purposes. An employer holding a valid A1 still has to file a Limosa declaration before the work starts, and an inspector will ask for both.
The proximity trap
Because Belgium is next door and the language is shared in Flanders, Dutch companies routinely treat a Belgian job as an extension of a domestic one. Short jobs get scheduled by a planner who has never heard of Limosa, and a technician drives down for a morning without a declaration in place.
The rule does not scale with distance or duration. There is no minimum number of days. A half-day call-out on a Belgian site is a posting, and unless it fits inside a specific exemption, such as urgent repair by a specialised technician limited to 5 days per month, it needs a declaration filed before the work starts.
The second proximity trap is the petrochemical turnaround. Large maintenance shutdowns pull in dozens of Dutch subcontractors at once, headcounts change daily, and the site is exactly the kind of high-value work where Check-in-at-Work applies. That is the scenario where informal crew substitution creates real exposure.
When does Check-in-at-Work apply?
Registration is mandatory for works on immovable property, excluding cleaning, and for certain meat-sector activities, where the total value of the works reaches 500,000 euro excluding VAT. The threshold applies whether that value is reached at the start of the works or during them, and it attaches to the works as a whole, not to your own contract value.
Three points that catch foreign contractors:
- It is daily. Registration must happen before the person begins work, every working day, for every person on site. It is not a one-off enrolment.
- Responsibility is shared. It lies both with the party sending the worker and the party doing the work, and the two must agree who registers and verify it happened. Assuming the main contractor covers you is not a defence.
- “Works on immovable property” is broad, reaching well beyond new-build into renovation, fit-out, technical installation and groundworks.
From 1 April 2027, a Programme Law adopted on 30 May 2026 extends the obligation to registering both entry and exit, and brings the supply of ready-mixed concrete into scope. Sign-in sheets will not carry you past that date.
The differences between the systems are set out in Limosa, Dimona or Check-in-at-Work.
What it costs to get wrong
Failing to file a Limosa declaration is a level 4 offence, the heaviest category in the Belgian Social Criminal Code, carrying the possibility of imprisonment alongside financial penalties.
Fines rose on 1 February 2026, when the Act of 19 December 2025 raised the multiplier applied to social criminal fines from 8 to 10. For some infringements the amount is multiplied by the number of workers involved, up to a maximum of 100, which is what turns one administrative gap on a ten-person crew into a serious figure.
There is a commercial cost too. Your Belgian client is exposed through joint and several liability for your workers’ wages, and through the withholding obligation: where a contractor has social or tax debts, the client must withhold 35 percent of each invoice excluding VAT for social security debts and 15 percent for tax debts, checked at checkinhoudingsplicht.be. Since 1 May 2026 a further 15 percent applies for outstanding self-employed contributions. A subcontractor who creates that problem does not get invited back. Our guide for main contractors covers the checks your client runs before awarding work.
Keeping the paperwork and the site in agreement
The hard part of cross-border work is not understanding the rules. It is keeping the file in your home office and the reality on a Belgian site aligned, week after week, as crews rotate and programmes move.
Two habits do most of the work. Treat every crew change as a compliance event: a new person means a new A1 check, a new Limosa entry and site registration under their own identity, arranged before they travel. And capture presence digitally at the moment someone arrives, tied to the person and the project, so the site record matches your declarations by default and you can produce a specific past day on request without reconstructing it.
Suivo’s check-in-at-work is used on Belgian sites where several subcontractors work side by side, and runs on the same workforce management platform as time tracking, so the data you capture for compliance also feeds hours and project costing instead of sitting in a separate system.
See how Van Moer manages registration across Belgian sites.
A note on language
Belgian filings and inspections in Flanders are conducted in Dutch, which removes the language barrier for most Dutch companies. In Wallonia and Brussels the working language will be French, so if you work across the language border, make sure your liaison person can operate in French or appoint someone who can.
Book a free demo
If you are bringing Dutch crews onto Belgian sites and want presence registration that satisfies an inspector without slowing your work down, we will show you how it runs day to day. Book a free demo.
