Slovakia sends fewer people to Belgium than Poland or Romania, but it has the most distinctive profile of any sending country: the overwhelming majority of Slovak postings are self-employed rather than employed. That single fact changes which rules apply to you and which mistakes are likely.
Where Slovakia sits in the Belgian market
Slovak companies and individuals filed for 5,393 posted persons into Belgium in 2023, 2.3 percent of the Limosa total, and Slovakia supplies 8 percent of all posting companies active in Belgian construction, a share far above its headcount share.
The reason is status. Almost seven in ten persons posted from Slovakia are self-employed (66 percent), and in the Belgian construction sector specifically the self-employed share of Slovak postings reaches 81 percent, the highest of any country. Slovak self-employed persons are the third-largest group of posted self-employed in Belgian construction, at 1,846 people.
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 Sociálna poisťovňa, the Social Insurance Agency before departure, one per posted worker, covering the full planned period. They prove your people stay in the Slovak 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.
Self-employed status is the thing that gets tested
With four in five Slovak construction postings being self-employed, the Belgian inspectorate’s attention naturally falls on whether that status is genuine. False self-employment is a central enforcement theme in Belgian construction, and a Slovak crew of nominally independent contractors working under a single principal’s direction, on their schedule, with their equipment, is the exact pattern that attracts scrutiny.
The practical implications are twofold. First, the self-employed exemption for business travel is limited to 5 days per month and covers business purposes, not the performance of construction work, so it will not cover a site posting. File the declaration.
Second, be able to evidence independence: your own contracts, your own equipment, control over how the work is done, and more than one client where that is the reality. If the arrangement is in substance employment, the consequences run beyond the Limosa file to social security liability and to your Belgian client, who can be drawn in through joint and several liability for wages.
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 what your Belgian client stands to lose.
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 B&R Bouwgroep manages registration across Belgian sites.
A note on language
Belgian authorities work in Dutch, French, German or English, not Slovak. Appoint a liaison person able to correspond in English at minimum, and in Dutch for Flemish sites.
For the wider picture for foreign employers in Belgium, see our guide covering every country and declaration.
Book a free demo
If you are bringing Slovak 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.
