The three-month notice period is mandatory, because:
- if the employee leaves, it benefits the business:
-- the employee has the time to hand over their work
-- the employer has time to look for and find a replacement, or prepare for work without the employee
- if the employee is fired, it benefits the employee:
-- they have the time to look for a new job
-- they continue working, receiving salary, and don't have to worry about bills, rent etc.
In both cases the employer and the employee can agree on the actual time when the employee quits: it could be the next day, or next week, or after three months, at the end of the notice period.
- if the employee leaves, it benefits the business:
-- the employee has the time to hand over their work
-- the employer has time to look for and find a replacement, or prepare for work without the employee
- if the employee is fired, it benefits the employee:
-- they have the time to look for a new job
-- they continue working, receiving salary, and don't have to worry about bills, rent etc.
In both cases the employer and the employee can agree on the actual time when the employee quits: it could be the next day, or next week, or after three months, at the end of the notice period.