Checkinatwork Compliance Guide 2026: Belgium's Construction Sector Attendance Registration Explained

The Checkinatwork system is Belgium's mandatory electronic attendance registration system for the construction sector. Introduced by the NSSO (RSZ/ONSS) to combat undeclared work on construction sites, Checkinatwork attendance registration is today a legal requirement for every Belgian construction employer. Who Must Comply with Checkinatwork? All employers and self-employed workers in the construction sector (NACE codes 41-43) must register the presence of every worker via the Checkinatwork system. This includes: - Main contractors and subcontractors on every construction site - Self-employed subcontractors active on construction sites - Temporary employment agencies supplying workers to construction firms - Foreign companies temporarily working on Belgian construction sites How Checkinatwork Attendance Registration Works 1. Site Registration: Every construction site must be registered in advance with the NSSO and receives a unique declaration number. 2. Mandatory Check-In: Every worker must be checked in before starting work — not retroactively. This is a hard deadline. 3. Check-In Channels: Via the NSSO online portal, the official mobile app, or automated systems like Checkin OK. 4. NISS Number Required: Every declaration requires a valid NISS/INSZ number for the worker. 5. Employer Responsibility: Employers are themselves responsible for monitoring their declarations. Penalties for Non-Compliance The NSSO enforces serious penalties for employers who fail to properly carry out Checkinatwork attendance registration: - Administrative fines from €50 to €2,500 per missing declaration - Social corrections of €6,000 per unregistered worker found during inspection - Criminal prosecution for repeated or systematic violations - Exclusion from public procurement contracts Practical Tips for Checkinatwork Compliance - Designate a compliance officer per construction site for attendance registration - Use an automated system that generates NSSO-compliant XML files - Weekly verification that all NISS numbers are valid - Keep all declaration confirmations as proof in case of inspection - Read our post on NSSO Attendance Declarations Explained for more context How Checkin OK Helps Checkin OK automates your complete Checkinatwork attendance registration. Upload your attendance lists in CSV or Excel format, and our platform automatically validates all NISS/BIS numbers, corrects errors via AI, and generates NSSO XSD v1.13-compliant XML ready for submission. No manual data entry, no errors, no fines. Frequently Asked Questions about Checkinatwork Q: What is the difference between Checkinatwork and CIAO? A: Checkinatwork is specific to the construction sector (NACE codes 41-43) and registers presence on construction sites with check-in only. CIAO is for the cleaning and meat processing sectors and requires both check-in and check-out times. Read more in our CIAO declaration guide. Q: Do I also need to submit Dimona alongside Checkinatwork? A: Yes. Dimona and Checkinatwork are separate obligations. Dimona registers the employment relationship (start/end of contract); Checkinatwork registers daily attendance on site. Both are mandatory in the construction sector in Belgium. Q: Can I avoid fines by using Checkin OK? A: Checkin OK minimises the risk of errors through automatic NISS validation and NSSO-compliant XML generation. However, the employer always retains final responsibility for timely submission. Try Checkin OK free today — automate your NSSO attendance registration and avoid costly fines.