The inhoudingsplicht (withholding obligation) means that before you pay a subcontractor for construction work in Belgium, you check whether that company has social or tax debts. If it does, you keep back part of the invoice and pay it straight to the government. The check takes a minute on checkinhoudingsplicht.be. You do it when you sign the contract and again before every payment. Skip it and you can owe the withheld amount twice and become liable for your subcontractor’s debts.
Suivo helps construction companies keep a reliable record of who works on site, including subcontractors, with Check in at Work registration. This guide covers the payment side: what to check, how much to withhold and where the money goes.
What is the inhoudingsplicht (withholding obligation)?
According to the RSZ (National Social Security Office), clients, contractors and subcontractors that have in-scope work done must check whether their (sub)contractor has:
- social debts with the RSZ, the construction fund PDOK/FBZB or the RSVZ (self-employed social security), or
- tax debts with FOD Financiën (Federal Public Service Finance).
If the check shows debts, you withhold a percentage of each invoice. You pay that amount to the RSZ (social part) or to FOD Financiën (tax part). You pay the rest to your subcontractor.
Two points often cause confusion:
- Private clients are excluded. A person who has work done purely for private purposes does not withhold. But a contractor renovating that person’s house must still apply the rule to its own subcontractors.
- Registration of contractors no longer protects you. The old “registered contractor” system was abolished on 1 September 2012. Today only the debt status at contract signature and at payment counts.
Which activities does it cover, and what changed in 2026?
The withholding obligation applies to:
1. Works in immovable property (werken in onroerende staat), such as building, renovation, demolition and installation work. Certain agriculture, horticulture and forestry activities are excluded. Cleaning of buildings also falls within “works in immovable property”.
2. Delivery of ready-mixed concrete (stortklaar beton).
3. Security and surveillance work under joint committee 317.
4. Certain meat-sector work.
The self-employed extension
The Programme Law of 22 December 2023 extended “social debt” to debts under the self-employed social status. This part applies only to works in immovable property, not to security or meat. The RSZ relaunched checkinhoudingsplicht.be on 1 May 2026 with new functions for this extension. According to the RSVZ, the self-employed withholding applies from 30 October 2026.
What this means for you:
- From that date, a self-employed tiler or electrician with unpaid social contributions can show a red status.
- The RSVZ does not count debts at or below an indexed threshold of EUR 2,647 (reference year 2026), debts whose payment term has not expired, or debts under a payment plan that is respected.
- Your check routine stays the same. The tool shows the correct percentage.
How do you check whether you must withhold (checkinhoudingsplicht)?
Use one of two official channels, according to the RSZ invoice FAQ:
- checkinhoudingsplicht.be: one company at a time, by company number (KBO), EU VAT number or another foreign identification number.
- BillRetainment: a secured web service for bulk or automated checks, useful if your accounting system pays many subcontractors.
The result is one of three statuses:
| Status | Meaning | What you do |
|---|---|---|
| Green (noObligation) | No debts that trigger withholding | Pay the full invoice |
| Red (Obligation) | Debts found | Withhold the percentage shown and pay it over |
| Grey (NotInDomain) | Company is outside the scope | No withholding |
Timing rules that matter:
- Check when the contract is concluded and before every invoice payment.
- Statuses are updated monthly, on the Friday after the last Thursday of the month. A green or grey status stays valid until the next update.
- A red status is valid only at the moment you consult it. FOD Financiën says that if you do not pay that same day, you must check again on the day you pay.
How much do you withhold, and where does the money go?
All percentages apply to the invoice amount excluding VAT.
| Part | Rate | Paid to |
|---|---|---|
| Tax debts | 15% | FOD Financiën, account BE63 6792 0036 4008 |
| Social debts (RSZ and/or PDOK/FBZB) | 35% | RSZ, account “Retenue Sociale Inhoudingen” BE76 6790 0001 9295 |
| Social debts (RSVZ, self-employed) | 15% | Same RSZ account |
| Social debts (both of the above) | 50% | Same RSZ account |
The total withholding for social and tax debts together can never be more than 50% of the invoice excluding VAT. When that cap is reached, the RSVZ 15% is not shown, but the subcontractor still owes that debt.
Practical points:
- Pay at the same time as the invoice. Use the structured reference that checkinhoudingsplicht or BillRetainment generates for the social part.
- Proof. For the social part, the database has evidential value, so a screenshot is not required. For the tax part, request a certificate (attest) from FOD Financiën and pay with the structured reference on it.
- Limitation certificate. For invoices of EUR 7,143 or more (excluding VAT), a subcontractor with debts can obtain a certificate that limits the withholding to its actual debt. It is valid for 20 days. The self-employed part has no such limitation.
- Payment plans. A company that obtained a payment deferral without court proceedings, or that strictly follows a final court decision, is exempt.
What happens if you forget: joint liability explained
Forgetting a withholding is expensive, and the cost lands on you, not on the subcontractor.
Direct sanctions
- Social part: you owe the RSZ the amount you should have withheld plus a surcharge of the same amount. In effect, you pay double.
- Tax part: FOD Financiën can impose a fine equal to double the amount that should have been withheld.
- Self-employed part: according to the RSVZ, the fine can be 15% of the total invoice amount, capped at EUR 10,578.23 for 2026, and that fine can itself turn your status red.
Joint liability (hoofdelijke aansprakelijkheid)
If your subcontractor had social debts when you signed the contract, you become jointly liable for them, according to the RSZ notice to contractors:
- Social liability is capped at the total price of the works excluding VAT, or 65% of that price if tax liability also applies.
- Tax liability is capped at 35% of the price of the works excluding VAT.
- Both cover debts that arise during the works as well.
- Liability does not apply if you correctly made and paid every withholding.
Chain liability
If the directly liable party does not pay within 30 days of a formal notice (or, for tax debts, a writ of execution), the upstream contractors become liable in turn. For a main contractor, that means a subcontractor’s subcontractor can become your problem. And if you do not pay a liability claim within the month after the RSZ’s formal notice, your own status can turn red.
Does it apply to foreign contractors?
Yes. Checkinhoudingsplicht shows the status of Belgian and foreign contractors. For a foreign subcontractor, enter its EU VAT number or another foreign identification number.
A foreign construction company that is not an active employer in Belgium can still be subject to withholding. This happens when it falls under joint committee 124 for bad-weather and loyalty-stamp contributions and has PDOK debts. Treat every foreign subcontractor exactly like a Belgian one: check before you sign, check before you pay.
For the other duties that apply to foreign firms, see our guide to posting non-EU workers to Belgium.
How the inhoudingsplicht, werfmelding and Checkinatwork fit together
These are three separate obligations with overlapping but different scopes:
| Obligation | What it does | Scope |
|---|---|---|
| Inhoudingsplicht | Protects the government from unpaid debts in the chain | Construction, ready-mix, security (PC 317), meat |
| Declaration of works (werfmelding) | Declares the site, the client and every subcontractor before the works start | Works in immovable property above the thresholds, ready-mix, security and meat |
| Checkinatwork | Registers every person on site each day before they start | Works in immovable property (not cleaning) on sites of EUR 500,000 or more excluding VAT, ready-mix delivery, meat |
From 1 April 2027, according to the RSZ, construction and ready-mix sites of EUR 500,000 or more move from Check in at Work to Check in and out at work (CIAO). Workers will register both arrival and departure. The RSZ says more details will follow.
Registering attendance does not replace the withholding check, and a green status does not replace attendance registration. What connects them is information. The declaration of works tells you which subcontractors are in your chain. Daily attendance records show who actually worked on site. With both, accounts payable can match every invoice to a declared subcontractor who was really there.
That is where a digital site record helps. Suivo registers attendance through an app, a mobile site pole with the Belgian ID card or a badge, or a vehicle black box, for your own crews and for subcontractors. B & R Bouwgroep, for example, says its staff “sign in easily with their badge” and estimates the saving at the equivalent of two FTEs (read the case).
A 5-step payment checklist for site managers and accounts payable
1. At contract signature: check the subcontractor on checkinhoudingsplicht.be and keep the consultation reference with the contract. A red status now means joint liability later.
2. Before the works start: make sure the subcontractor is in the declaration of works, including any subcontractor it brings in.
3. When the invoice arrives: match it to the declared contract and to the attendance records for that subcontractor.
4. On the payment day: check the status again. If it is red, withhold the percentage shown, excluding VAT, and pay it at the same time as the invoice with the correct structured reference.
5. File the evidence: keep the invoice, the consultation reference or FOD certificate, and the payment proof together. Repeat for every invoice, not only the first.
A simple rule for accounts payable: no fresh check on the payment day, no payment.
Frequently asked questions
What is the inhoudingsplicht?
The inhoudingsplicht (withholding obligation) requires clients and contractors in construction, security and certain meat work to check whether their (sub)contractor has social or tax debts. If it does, they must withhold part of each invoice and pay it to the RSZ or FOD Financiën instead of to the subcontractor.
What does inhoudingsplichtig mean?
A company is inhoudingsplichtig (subject to withholding) when checkinhoudingsplicht.be shows a red status for it. Anyone paying that company’s invoice for in-scope work must then withhold the percentage shown.
What are the new rules for the inhoudingsplicht?
According to the RSVZ, from 30 October 2026 social debts will also include debts under the self-employed social status, for works in immovable property only. That part means a 15% withholding, and the total withholding stays capped at 50% of the invoice excluding VAT.
How can I check whether there is a withholding obligation?
Enter the company number, EU VAT number or foreign ID of the (sub)contractor on checkinhoudingsplicht.be, or use the BillRetainment web service for bulk checks. A green or grey status means no withholding; a red status tells you the percentage to withhold.
Does the inhoudingsplicht apply to private individuals?
No. A private person who has work done purely for private purposes does not have to withhold. The contractor working for that person must still apply the rule when it pays its own subcontractors.
Know who worked on your site before you pay
The withholding check protects your cash. A reliable attendance record shows which subcontractors were really on your site, and when. Suivo gives you that record for your own crews and your subcontractors, in the same platform as your time registration. See how it works on your sites.
