Knowledge base
Practical guides on the Belgian withholding obligation.
Checking a supplier's tax debts in Belgium: how it works
An NSSO check alone is not enough. How to check whether a supplier owes tax to the Belgian FPS Finance, when to withhold 15% and what proof to keep.
Declaration of works to the NSSO: when, how and why
Anyone having immovable works carried out in Belgium must declare them to the NSSO beforehand. Here is who declares, within what deadline, through which channel and what happens if you forget.
Supplier subject to withholding: what to do at payment
Your check flags the withholding obligation. Here is how much to withhold, who to transfer it to, which certificate can lower the amount and what proof to keep.
Check a Belgian VAT number: making sure a supplier really exists
A VAT number on an invoice proves nothing until you check it. Here is how to verify a Belgian or European number, which sources are official and what still needs checking.
Article 30ter explained: meat and security
Article 30ter extends the withholding obligation to the meat sector and to security services. Which activities, which rates and where it goes wrong.
Requesting an NSSO certificate: who, where and how long it is valid
Step by step: which document you need for a withholding obligation check, where to request it and how long it stays valid.
How to find your supplier's NSSO number: a guide for clients
Finding your supplier's NSSO number is the first step of every withholding obligation check. Here are the four most reliable ways, plus the pitfalls to avoid.
Checking social security debts: step by step
How to correctly check a contractor's social security and tax debts: what you need, how to read the result and what to do when an amount must be withheld.
Article 30bis explained: withholding obligation and joint liability
What article 30bis of the law of 27 June 1969 actually says: who must withhold, how much, and which evidence you have to keep.
Belgian withholding obligation for contractors: complete 2026 guide
Everything about the Belgian withholding obligation in 2026: when to check, how much to withhold, who to pay and how to avoid penalties.