Under Belgian Law, the working time schedules of part-time workers are to be properly kept and respected by the employer. Strict rules apply in case of modifications of the working time schedules. If these rules are not complied with, the part-time workers are presumed to work as fulltime workers. However, the Supreme Court recently ruled that the aforementioned presumption only applies for the benefit of the institutions and government officials, which are empowered to prevent and obstruct undeclared work. As a result of this judgement, part-time employees cannot invoke the presumption in order to claim fulltime salary and should always be able to prove their actual (fulltime) performances in order to obtain additional pay.