Around 4% of workers are entitled to an ONSS reduction that is not applied.
The average amount to be recovered through this reduction is of €2200.

Hopefully it is still time to get your old ONSS reductions back!

Acerta explains all about how employers can beneficiate from a full range of subventions for their employees in its article “Récupérer les réductions ONSS du passé ? Il n’est pas trop tard !” (Only available in FR).