An ancillary activities clause is a clause in the employment agreement that prohibits an employee to carry out other activities. An ancillary activities clause can entail a general prohibition, or a prohibition to carry out activities that are not compatible with the activities that are carried out for the employer. The clause can also be worded in such a way that ancillary activities may only be carried out upon approval.

For an employer, it may be advisable to include in the employment agreement that an employee may only carry out ancillary activities after consent has been given in this respect, so as to prevent violation of the Working Hours Act (because the employee combines several jobs).