On 1 April 2014, the so-called obligation to state reasons was introduced in Belgian dismissal law.
This does not imply that the reason of the dismissal needs to be specified in the notice of termination. The reason of dismissal is only notified when the employee explicitly asks for this.
The employee needs to request this by registered letter within 2 months after the end of the contract of employment. The employer then has 2 months to respond by registered letter.
If the employer does not answer or not on time, the employee can demand damages of 2 weeks of pay. If the reason is false or too light, the employee can demand damages of 3 to 17 weeks of pay.
Remark:
What does have to be specified in the notice of termination is the beginning and the term of the period of notice. If not, it is considered an invalid notice of termination and the employee can demand payment in lieu of notice.