Art III.51 §1 a.f. of the CDE concerning the CBE and one-stop-shops for enterprise registration specifies:
Notwithstanding the provisions of paragraph 2, commercial, artisanal and non-commercial enterprises under private law which intend to exercise an activity other than that for which they were registered must first request modification of their registration in the Crossroads Bank for Enterprises. This obligation applies in the same way for commercial, artisanal and non-commercial enterprises under private law which intend to set up a new business unit in Belgium.
Art XV.77 of the CDE specifies various fines in case of non-compliance with this rule.
Since the CBE is the central database for various administrations, the risk of being found out is real. Do not hesitate to contact one of our Formalis one-stop-shops for enterprise registration if you have the slightest doubt. It costs nothing to find out.