When your employees check in or out via the Check In and Out at Work system (CIaO) — whether through the official NSSO app with a QR code, or through a commercial solution that connects to it — the NSSO automatically checks every registration. If something doesn't match, the NSSO attaches a code to that registration: a so-called "remark". Those are the NSSO error codes that probably brought you here.
What exactly is the CIaO system?
CIaO stands for Check In and Out at Work, the NSSO's online service used to register presence on construction sites and at certain services. Every registration is checked against other data sources the NSSO has access to: your Dimona declarations (for your own staff), Limosa notifications (for foreign workers), and the Declaration of Works (for the contractor/subcontractor structure on the site). When a registration doesn't match what's in those sources, or when a technical problem occurs (such as a missing GPS location), the system generates an error code.
How are the codes structured?
The official NSSO list simply uses consecutive numbers (not every number is in use — there are deliberate gaps in the sequence). In the CIAO Assist error code guide, we give each code a recognizable label in the form CAW_1, CAW_2, and so on, so you can find and discuss them more easily with your team. Roughly, the codes fall into a number of groups:
- Dimona-related (including CAW_1, CAW_2, CAW_3, CAW_4, CAW_5, CAW_16): the relationship between the employee and the company doesn't match, usually due to a missing or incorrect Dimona declaration.
- Limosa-related (CAW_6 through CAW_9): applicable to foreign workers without an (active) Limosa notification.
- Declaration of Works (CAW_10, CAW_11, CAW_12, CAW_17): the site or the contract with the company is not correctly declared in the Declaration of Works.
- Registration behavior (CAW_21, CAW_22, CAW_24): duplicate check-in or check-out moments, or a missing counterpart within 24 hours.
- Location and technical (CAW_25, CAW_32 through CAW_38): missing or incorrect GPS coordinates, a registration transmitted too late, or an address that can't be found.
The complete, literal list of all 26 official codes — including the cause and recommended action per code — can be found in our error code guide.
Is an error code the same as a fine?
No. An error code is not a sanction in itself — it's a signal that something deserves follow-up. Some codes point to an innocent mistake (for example, an employee who accidentally checks in twice), others to something you should actually correct (for example, a late Dimona declaration). The risk isn't in the code itself, but in the fact that many companies only discover during an inspection which codes have been accumulating for months.
How do you find your own error codes?
CIAO Assist reads the results of your registrations via the official NSSO connection and translates them into a clear overview: which codes are present, for whom, and since when. Want to know this for your own organization? Start a free CIAO Check — that gives you a first concrete overview with no obligation.
What do you do with an error code?
Every code in our error code guide comes with a brief explanation of the possible cause and the recommended action. For most codes, it's enough to check the underlying declaration (Dimona, Limosa, or Declaration of Works) and correct it if necessary. If it remains unclear, you can reach us directly via the contact page.