For new hires, it is helpful to have a probationary period (usually 3 months) during which the employee can be assessed. It is unusual to use a probationary period when an existing employee enters into a new employment contract. You can decide how long you want the probation period to be. The option to extend the probationary period is helpful when employees have not achieved set targets or have performed poorly during the initial period or have been absent. Probationary periods will not stop the employee from gaining unfair dismissal rights when they reach the qualifying service.