Students from a non-EEA country?
It is not necessary to request a work permit type C anymore. As from January 1st 2019 this work permit is no longer issued.
If you have a legal residence in Belgium and you want to work as a student, having an electronic residence permit is sufficient. As of January 1st 2019 residence permits issued for non-EEA students will contain information about the eligibility to work in Belgium.
In case you received an annex 15 from the city hall while waiting for your actual residence permit card, you can also use this document to work in Belgium.
As a non-EEA citizen, you cannot work more than 20 hours per week during the academic year. During official holiday periods (i.e. winter, spring or summer holidays), this limitation does not apply, therefore, you can work more than 20 hours per week.
If you arrive in Belgium during the summer before the start of the academic year in which you will start your studies, you are not allowed to work during this time.
Did you arrive in Belgium before 2019 and you have a work permit type C?
If you already have a work permit type C that is still valid, you can still use this permit to work.
Did you arrive in Belgium before 2019 and you currently do not have a work permit type C?
The electronic residence permit you received before 2019 does not mention additional information regarding your employment possibilities. You can apply for a new residence permit at the city hall (for free). Or you can give your employer a copy of your residence permit and an attestation of registration at the university or university college.