As discussed in the chapter on leave the annual leave period is between May 1st and September 15th. The manager has to inform the employee as soon as possible when the leave is granted or at the latest April 1st.
It can happen that the leave collides with the term of notice, if the employee has for example been made redundant or they has resigned after the annual leave was decided. If this is the case the employer/manager and the employee must negotiate how to handle the leave. Whatever the conclusion is, the employer cannot single-handededly decide that the employee takes his leave during time of notice. The employee must give their concent on that. This rule does not appear in any laws or collective wage agreements but is built on judicial enforcement.
If the annual leave is taken during the notice period the notice period shall be extended by the time of the annual leave. If the employee is not to expected to work during their period of notice it is common practice that the two parties negotiate that the employee gets pay in lieu of notice.