Belgian withholding obligation for contractors: complete 2026 guide

The withholding obligation is the main financial check every principal or main contractor in Belgium must run before paying a subcontractor. In 2026, getting it wrong exposes you to joint liability for your subcontractor's social and tax debts, on top of an administrative fine equal to 35% or 15% of the invoice. This guide explains what the rule is, when it applies, how much to withhold, and how to automate the entire process.

What is the withholding obligation?

It is a preventive measure set out in articles 30bis and 30ter of the Belgian law of 27 June 1969. Before paying a contractor's invoice, you must check whether that contractor has, at that very moment, social debts with the NSSO or tax debts with the FPS Finance. If so, you cannot pay the full amount: you withhold a legally defined percentage and transfer it directly to the relevant authority.

The intent is simple: prevent principals from outsourcing work to companies that fail to pay their contributions and taxes. By placing the burden on the payer, the chain stays financially healthy and social fraud shrinks.

See also the FAQ for worked examples.

When does the obligation apply?

You are subject to withholding once three conditions are met:

1. You pay an invoice to a contractor or subcontractor.
2. The invoice covers works listed in article 30bis or 30ter.
3. The payment is part of your professional activity. Purely private orders by a natural person are excluded.

It does not matter whether the invoice is a deposit, a progress bill or a final one: every payment is checked separately. If you are yourself a subcontractor, the same rule applies in the other direction for whoever pays you.

Which sectors are covered?

Articles 30bis and 30ter cover four sectors today. See the dedicated page for the exact scope:

• Construction and real estate: new build, renovation, demolition, installations, ready-mixed concrete. Learn more.
• Cleaning: building maintenance, windows, industrial cleaning.
• Meat: cutting, deboning, slaughter, preparations.
• Security: surveillance and guarding services.

Several agricultural, horticultural and forestry activities are explicitly excluded. When in doubt, the NSSO returns a sector qualification you can review on every check via Checkplicht.

How do you check a contractor?

Checks run through the NSSO and FPS Finance official web services. Two approaches:

1. Manually via the public portals. Workable for one or two enterprise numbers, but slow and error prone at scale, and you have to record the date and outcome yourself.
2. Automatically through a service that queries the web service and archives the proof. That is what Checkplicht does: you enter the enterprise number, we fetch the live status from NSSO and FPS, compute the withholding, and produce a control certificate with a unique ID and QR verification.

Note: the certificate is valid at the moment of payment. Paying a few weeks later means running the check again. Checkplicht does that on the cadence you pick (7, 14 or 30 days).

Withholding percentages in 2026

Percentages are set by law and applied on the VAT-excluded invoice amount:

• 35% if the contractor has social debts (paid to the NSSO).
• 15% if the contractor has tax debts (paid to the FPS Finance).
• 50% cap: if both types of debts exist, the total withholding is capped at 50% of the invoice excluding VAT.

Since 2026 the cap applies explicitly and you must compute the cumulative amount for every invoice. Checkplicht enforces the cap and shows NSSO, FPS and combined amounts.

Penalties for non-compliance

The penalty is a double hit:

• Joint liability for the unpaid social and tax debts of your contractor, up to the invoice amount excluding VAT.
• Administrative fine equal to the amount you should have withheld, i.e. 35% or 15% of the invoice, capped at 50% combined.

On a 100,000 euro invoice, a missed check can therefore cost up to 150,000 euros: 100,000 liability plus 50,000 fine. More detail in the FAQ.

Practical steps for your accounting

1. Add every contractor by enterprise number as soon as you accept a quote.
2. Check on invoice receipt, not only at payment time.
3. Split the payment: net amount to the contractor, withheld part to the NSSO with the structured reference +++, and/or to the FPS with its own structured reference.
4. Archive the proof alongside the invoice. Social inspections can look back up to four years.
5. Schedule periodic rechecks for recurring contractors. Checkplicht runs these automatically.

Automating with Checkplicht

Beyond a handful of contractors, manual checks become unmanageable. Checkplicht centralises everything:

• Live NSSO, FPS Finance and INASTI checks from the enterprise number.
• Automatic rechecks at your chosen cadence, with alerts when a contractor becomes subject to withholding.
• Control certificates as PDF with unique ID and QR verification.
• Payment instructions with QR codes for NSSO and FPS, structured references included.
• Excel import and export for your full contractor portfolio.

See pricing or start free with 14 days and no card. Want a walkthrough? Get in touch.

Frequently asked questions

All answers on withholding, control certificates, penalties and payments live in the FAQ. See also How it works for a product walkthrough.