As you know, it is relatively inexpensive to employ students in Belgium because you and they pay less social security than other employees – the employer pays 5.42 % of gross salary and the student pays 2,71 %. From now on however the ONSS may ask you to provide proof that the person you employ is actually a student. So when you’re setting everything up, make sure to ask them to provide a proof of their student status and keep a copy on file.
Source: SDWorx