29 CFR § 825.313 - Failure to provide certification.
(a) Foreseeable leave. In the case of foreseeable leave, if an employee fails to provide certification in a timely manner as required by § 825.305, then an employer may deny FMLA coverage until the required certification is provided. For example, if an employee has 15 days to provide a certification and does not provide the certification for 45 days without sufficient reason for the delay, the employer can deny FMLA protections for the 30-day period following the expiration of the 15-day time period, if the employee takes leave during such period.
(b) Unforeseeable leave. In the case of unforeseeable leave, an employer may deny FMLA coverage for the requested leave if the employee fails to provide a certification within 15 calendar days from receipt of the request for certification unless not practicable due to extenuating circumstances. For example, in the case of a medical emergency, it may not be practicable for an employee to provide the required certification within 15 calendar days. Absent such extenuating circumstances, if the employee fails to timely return the certification, the employer can deny FMLA protections for the leave following the expiration of the 15-day time period until a sufficient certification is provided. If the employee never produces the certification, the leave is not FMLA leave.
(c) Recertification. An employee must provide recertification within the time requested by the employer (which must allow at least 15 calendar days after the request) or as soon as practicable under the particular facts and circumstances. If an employee fails to provide a recertification within a reasonable time under the particular facts and circumstances, then the employer may deny continuation of the FMLA leave protections until the employee produces a sufficient recertification. If the employee never produces the recertification, the leave is not FMLA leave. Recertification does not apply to leave taken for a qualifying exigency or to care for a covered servicemember.
(d) Fitness-for-duty certification. When requested by the employer pursuant to a uniformly applied policy for similarly-situated employees, the employee must provide medical certification, at the time the employee seeks reinstatement at the end of FMLA leave taken for the employee's serious health condition, that the employee is fit for duty and able to return to work (see § 825.312(a)) if the employer has provided the required notice (see § 825.300(e)); the employer may delay restoration until the certification is provided. Unless the employee provides either a fitness-for-duty certification or a new medical certification for a serious health condition at the time FMLA leave is concluded, the employee may be terminated. See also § 825.213(a)(3).