Specific measures against social fraud

A (sub)contractor may have tax debts towards the FPS Finance or social security debts towards the National Social Security Office (NSSO), the Employers’ Service for Organisation and Control of Subsistence Security Schemes (OPOC/PDOK), the Social Fund of the Security Sector (FSEG/FBZB) or the National Institute for the Social Security of the Self-Employed (RSVZ/INASTI). In such a case, you are required to withhold part of the invoices. The remaining amount must be paid to the (sub)contractor. 

What is meant by ‘Withholding obligation on invoices’? 

Clients, contractors and subcontractors who have activities carried out as described below are required to check whether their (sub)contractors have social and/or tax debts. If this is the case, they have to withhold a certain percentage of the invoice amount (exclusive of VAT) and transfer it to the bank account "Retenue Soc Inhoudingen" (for social debts) and/or to the FPS Finance bank account (for tax debts). 

The website Checkobligationderetenue (in French) allows you to check whether the (sub)contractors have social or tax debts. 

Which activities are covered by the withholding obligation on invoices?

The withholding obligation on invoices covers:

• Works on immovable property (art. 30bis of the Law of 27 June 1969), with the exception of certain agriculture, horticulture and forestry activities which are explicitly excluded from the area of application. 
• The supply of ready-mixed concrete, referred to in Article 1, a, fifth paragraph, indent 28 of the Royal Decree of 4 March 1975 establishing and determining the name and the competence of the joint committee ('paritair comité') of the construction industry and determining the number of its members. 
• Works falling under the Joint Committee for Security and/or Surveillance Services (art. 30ter of the Law of 27 June 1969 - Royal Decree of 17 July 2013). 
• Activities in the meat sector (art. 30ter of the Law of 27 June 1969 - Royal Decree of 22 October 2013). 

The obligation to withhold part of the invoice for social security debts relating to the ‘self-employed’ social status only applies to works on immovable property.  

Tax debts with the FPS Finance 

If the contractor has tax debts, 15% of the invoice amount (exclusive of VAT) has to be deducted and transferred to the FPS Finance (account number BE63 6792 0036 4008 with BIC: GEBABEBB).

Social debts  

If the (sub)contractor has social security debts towards the NSSO, OPOC/PDOK or FSEG/FBZB, 35% of the invoice amount (exclusive of VAT) must be withheld.   

If the (sub)contractor has social security debts towards the RSVZ/INASTI, 15% of the invoice amount (exclusive of VAT) must be withheld.‌  

The total amount being withheld may not exceed 50% of the invoice amount. The system takes this into account when displaying the percentages to be withheld by not showing the RSVZ/INASTI status (15%) when tax debts towards the FPS Finance and social security debts towards the NSSO, OPOC/PDOK or FSEG/FBZB are also present. The debt towards the RSVZ/INASTI remains due, but will not be displayed as a temporary measure. The RSVZ/INASTI status (15%) will be displayed again as soon as the situation allows the system to do so, without the 50% threshold being exceeded. 

Any amounts withheld from invoices for social security debts must be transferred directly to the bank account named ‘Retenue Soc Inhoudingen’ (IBAN: BE76 6790 0001 9295; BIC: GEBABEBB). 

Consult the ‘Manual Withholding obligation’ for a step-by-step guide on how to proceed in detail.

You can use the Declaration of works online service to notify the NSSO and relevant inspection services of certain activities being carried out.

Which works do you have to declare?

For works on immovable property and the supply of ready-mixed concrete (30bis), you have to declare: 

• any ‘client – contractor' contract from 30,000 euros (exclusive of VAT);
• any ‘client – contractor' contract from 5,000 euros (exclusive of VAT) with at least 1 subcontractor;
• any ‘client – contractor' contract with at least 2 subcontractors;
• hazardous work due to the presence of asbestos.
  Where the works concern a temporary or mobile construction site or the removal of asbestos, the declaration must be made at least 15 calendar days prior to the start of the works. 

Work covered by the Joint Committee for Security and/or Surveillance Services and certain activities in the meat sector (30ter) also have to be declared to the NSSO as soon as there is any activity carried out.

When should the declaration be submitted?

The declaration has to be submitted before work starts.

How to submit a declaration? 

The online service Declaration of works is available on the Declaration of works page of the Social Security Portal site (in French). 

More information can be found in the ‘Manual Declaration of works’ which sets out all the steps in detail.

'Check in at work' is an online platform provided by the NSSO to ensure that employers register the attendance of their workforce correctly. 

What is Check in at work?

Check in at work is the online service for the attendance registration concerning the supply of ready-mixed concrete, activities falling under the meat sector and for works on immovable property, with the exception of certain agricultural, horticultural and forestry activities that are explicitly excluded from the area of application. It concerns the registration of:

• anyone who carries out, before 1 April 2024, activities on immovable property (with the exception of cleaning activities) at a workplace with a total cost equal to or exceeding 500,000 euros (exclusive of VAT); 
• anyone who carries out activities related to meat preparations or meat products and the slaughter or cutting of hoofed animals, poultry and rabbits in establishments subject to the approval (approvals, authorisations and prior registrations) of the Federal Agency for the Safety of the Food Chain (FASFC).

Via Check in at work, employers and contractors register the attendance of their own employees, their subcontractors and their independent subcontractors. Employees and independent subcontractors can also register themselves on their own in the system.

Registration must be made on a daily basis and before the person carrying out the activities starts work. 

Workplaces covered by the compulsory attendance registration via Check in at work must be declared in the online service Declaration of Works (in French).

More information on foreign employees or employers is available on the Check in at work page on the website Working in Belgium. 

'Check in and out at work' is the NSSO's online service for registering attendance at work in selected sectors. For the time being, you can use the online service for work in the cleaning sector.

As from 1 April 2027 the online service will also be used for other types of works on immovable property (construction, electrics, carpentry, earthworks, etc.).

What is Check in and out at work for the cleaning sector?

As from 1 September 2024 the registration of the start and end of activities and breaks is mandatory for every employee carrying out certain cleaning activities. It only concerns 'activities whose purpose is to clean a property on behalf of a third party' and for which the total amount (exclusive of VAT) is equal to or exceeding the following threshold:

• 30,000 euros without a subcontractor;
• 5,000 euros with 1 subcontractor;
• no limit for 2 or more subcontractors. 

Registration therefore becomes mandatory when a chain declaration in the declaration of works (in French) online service is required.

There are two types of registration: In and Out. Registration 'In' should be done when the person carrying out the activities starts work. Registration 'Out' should be done at the end of the activities. Breaks must also be registered.

What does Check in and out at work mean for other types of works on immovable property?

As from 1 April 2027 attendance registration will be extended to everyone carrying out specific works on immovable property (with the exception of cleaning activities) and the supply of ready-mixed concrete at a workplace for which the total cost, excluding VAT, is equal to or exceeds 500,000 euros.

Two types of registration will apply: In and Out. The ‘In’ registration must take place when the person carrying out the works arrives at the workplace. The ‘Out’ registration must take place when the person carrying out the works leaves the workplace.

Who is responsible for registrations in Check in and out at work?

Employees, self-employed workers, temporary agency workers, students and trainees self-register their presence at the workplace at the site and without delay. As an employer, you cannot do the registration. However, you must provide registration resources. You have a choice of channels, and you may also combine a number of channels.

As an employer, you can access the registrations of your own employees and those of your subcontractors.
You have access via the Check in and out at work online service on Working in Belgium.

In addition to consulting registrations, you can also report certain errors in a registration. Contact the NSSO within 30 days of the registration date to request a change.

Access to Check in and out at work

To access the secure online service Check in and out at work as a company, it must be registered with the Crossroads Bank for Enterprises.

You also need an approved digital key, i.e. MyGov.be, itsme, eIDAS or email (‘TOTP’).

Here are the approved digital keys:

1. MyGov.be: If you have a Belgian electronic identity card, you can use this digital key. However, you will need to install the MyGov.be app on your smartphone. For more information, please visit the help centre page of the MyGov.be website. 
2. itsme: If you have a Belgian electronic identity card (eID), you can use this digital key. However, you have to install the itsme app on your smartphone. For more information, please visit the itsme page of the CSAM help centre.
3. eIDAS: If you don't have a Belgian identity card but you do have another approved European electronic proof of identity, you can use this digital key. To find out whether your electronic proof of identity authorises you to log in, click on ‘Log in with an electronic identification means recognized at European level’. You will then get an overview which member states already have an electronic proof of identity.
   Please note: In order to use eIDAS, you are required to identify yourself to this service. For this, you will need your European electronic proof of identity, your email address and phone number. More information can be found on the eIDAS page of the CSAM help centre.
4. E-Mail TOTP: Your country doesn't support the digital keys itsme or eIDAS and/or you don't have a Belgian national identification number (BIS number)? Then make an appointment for a video call with Sigedis, the partner of the social security institutions for personal identification. Please make an appointment on the belgianID-website. After checking a number of documents, Sigedis will determine whether you already have a BIS number. If you don’t have one, Sigedis will create a number for you. During your video call, Sigedis will help you to obtain a digital key.

Log in to CSAM with your company registration number, your BIS number and your digital key. As the legal representative of your company, you can appoint yourself as Chief Access Manager to manage access to your online services. As Chief Access Manager, you determine which employees have access to Check in and out at work. You can also appoint employees as access managers to assist you with administration.

The procedure information on this page was funded by the European Union.

Funded by the European Union – NextGenerationEU. Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or European Commission. Neither the European Union nor the European Commission can be held responsible for them.

Social Security Contact Centre

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