What about subcontractors and third parties for Check-in-at-work?

Short answer: the employer or contractor registers their own employees, their subcontractors and their self-employed subcontractors. Workers and self-employed subcontractors can also register themselves. It has to happen every day, before the person starts work.

Who registers whom

This is the part that causes most of the confusion on site. Check-in-at-Work is not “everyone registers themselves”. The obligation sits with the employers and contractors working on the site: they register the presence of their own employees, of their subcontractors, and of their self-employed subcontractors. Workers and self-employed subcontractors are additionally allowed to register themselves in the system.¹

In practice that means a main contractor cannot assume a subcontractor has taken care of it. If you brought a party onto the site, their presence has to appear in the registration.

Which sites this applies to

Check-in-at-Work covers three activities:¹

• Works in immovable state – construction work on a site, excluding cleaning activities and certain explicitly excluded agriculture, horticulture and forestry activities
• Delivery of ready-mix concrete
• Meat sector activities – preparing meat products, and slaughtering or cutting hoofed animals, poultry and rabbits, in establishments approved by the FAVV/AFSCA

For construction, the obligation only kicks in above a threshold. For works started after 29 February 2016 the threshold is 500,000 euro excluding VAT for the total value of the works on that site. Works that started between 1 April 2014 and 29 February 2016 used a threshold of 800,000 euro.²

The site also has to be declared in the Aangifte van werken (works declaration). The RSZ then sends every declared party a warning letter, reference CAWON, confirming that registration is required for those works.^2,3

When the registration has to happen

Daily, and before the person carrying out the works starts working.¹ It is not a end-of-week administrative exercise, and it cannot be completed retroactively after an inspector has been on site. This is the single most common reason registrations are found non-compliant.

Foreign contractors and parties from abroad

If you are a foreign contractor and you contract directly with a Belgian client for works in immovable state, the same registration obligations apply to you and to the people you bring onto the site.¹ Being established outside Belgium does not remove the obligation, and the main contractor remains exposed if a foreign subcontractor’s people are not registered.

What changes on 1 April 2027

This is the part worth planning for now. The Programmawet of 30 May 2026 (title 6, chapter 1, articles 124 to 131) makes IN and OUT registration mandatory for works in immovable state – excluding cleaning activities – and for the delivery of ready-mix concrete, on sites where the total value is 500,000 euro excluding VAT or more.¹

The obligation takes effect on 1 April 2027, deliberately delayed to give employers time to prepare. From that date it will no longer be possible to register attendance for works in immovable state in Check-in-at-Work: those registrations move to Check in and out at work (CIAO).¹

So if you run construction sites above the threshold, you are not looking at a tweak to your current process. You are looking at recording departures as well as arrivals, on every site, from a fixed date.

What this means for how you organise it

Three things follow from the rules above:

• You need one register per site, not one per company. Because you are responsible for subcontractors and self-employed subcontractors you brought in, a system that only covers your own payroll leaves you exposed.
• It has to work before the shift, on site. A daily, pre-start obligation means the registration method has to survive real site conditions rather than depend on someone in the office.
• Assume check-out is coming. Anything you choose now for sites above 500,000 euro should be able to record an OUT as well as an IN before April 2027.

Sources

1. RSZ/ONSS, Checkinatwork (including the alert of 30 July 2026 on Check in and out at work from 1 April 2027).
2. RSZ/ONSS, Werken in onroerende staat – drempelbedragen.
3. RSZ/ONSS, Aangifte van werken.
Checked against the official sources on 30 July 2026. Thresholds and dates change – verify against the RSZ pages before relying on them for a specific project.