Under the Family and Medical Leave Act (FMLA), an employer may be estopped from denying an employee’s entitlement to leave under certain circumstances if the doctrine of FMLA estoppel applies.  FMLA estoppel is based on the doctrine of equitable estoppel.  Under equitable estoppel, a party who makes a representation that misleads another person, who then reasonably relies on that representation to his detriment, may not deny the representation.  In the context of the FMLA, this means that an employer may be barred from asserting an affirmative defense contesting an employee’s entitlement to FMLA leave if the employer’s words or conduct misled the employee into relying on the leave.
FMLA estoppel is not available to an employee unless the employee first triggers the protections of the FMLA by providing his or her employer with notice that he or she may need FMLA leave.  The employee must also show that he or she reasonably believed that the employer authorized FMLA leave, as opposed to some other kind of leave.  See Murphy v. FedEx National LTL, Inc., 618 F.3d 893 (8th Cir. 2010).
Takeaway for Employers:  When an employee provides sufficient notice that he or she may need FMLA leave, the employer should be careful to avoid words or conduct indicating that the employee is entitled to FMLA leave before gathering all of the facts necessary to determine whether the employee qualifies for FMLA leave.