Irish companies working in Belgium are typically in technical services, engineering, ICT and specialist installation rather than general construction. Volumes are modest, and because Ireland shares a language with much of Belgian business, there is a persistent assumption that formalities will be light. They are not.
Where Ireland sits in the Belgian market
Ireland falls within the ‘other countries’ group of the Belgian Limosa breakdown, which together accounted for 36,254 posted persons in 2023.
Irish activity concentrates in professional, technical and installation work, with a smaller presence in the construction and metalworks sectors that dominate the Polish and Dutch flows. Assignments tend to be shorter and more specialised, which is precisely the profile that leads companies to wonder whether an exemption applies.
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 Department of Social Protection before departure, one per posted worker, covering the full planned period. They prove your people stay in the Irish 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.
Short technical visits and the exemption that usually does not fit
Irish companies most often ask whether a two- or three-day technical visit needs a declaration. The honest answer is usually yes.
The exemptions that look relevant are narrow. Initial assembly or installation of goods you supplied is exempt for a maximum of 8 days, and only for qualified or specialised workers. Urgent repair or maintenance by specialised technicians is exempt for a maximum of 5 days per month. Attending meetings in a restricted circle is exempt up to 60 days a year, with no single meeting over 20 successive days, but that covers attending meetings, not performing work.
A short engineering visit to commission, troubleshoot or configure something on a client’s premises will often fall outside all three. And because the consequence of relying on an exemption that does not hold is a level 4 offence, the cost-benefit is one-sided: filing is free and takes minutes.
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 explains how your paperwork is judged on the Belgian side.
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 Cibor manages registration across Belgian sites.
A note on language
English is widely used in Belgian business and is accepted by the authorities for many purposes, which is a genuine advantage. Be aware, though, that a site inspection in Flanders will be conducted in Dutch and in Wallonia in French, so a local liaison person is still worth having.
For the wider context on posting into Belgium, see the complete guide for foreign employers.
Book a free demo
If you are bringing Irish 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.
