Upon departure or a few days earlier, you have to deregister yourself as a resident of Antwerp.
The procedure is as follows:
Observation: Do not forget to mail the document!
If you send the document on a later date than the date of departure (= ‘from’ date on the application document), the official date of deregistration will be the date of receipt, not the date of departure.
!Do not forget to deregister, otherwise you continue to be a Belgian resident according to the Belgian authorities (tax offices, etc.)!