It depends on why the employee needs leave. If the employee knows well in advance when he or she will need to take leave, the employee must give at least 30 days' notice. For example, if an employee has surgery scheduled in two months, that employee can give the required notice. If, however, the employee needs leave for an emergency, the employee is required to give only as much notice as is practicable under the circumstances. For example, an employee who is hit by a car should inform the employer as soon as it is practical to do so.
Under revised regulations issued in 2008, an employee who wants to use accrued paid leave during FMLA leave must follow the notice requirements of the employer's policy. If the employer's policy requires one week of advance notice to use vacation time, for example, the employee must provide that notice. If the employee has a medical emergency and cannot give any advance notice, the employee is still entitled to FMLA leave, but may not take paid leave until the employer's requirements are met. For more information on the FMLA's notice requirements, see Nolo's article FMLA Regulations Change Rules on Notice and Certifications.