Can FMLA leave be designated retroactively?

Generally, no. If an employer has enough information to know that an absence qualifies for FMLA but fails to notify the employee, the leave cannot be retroactively designated as FMLA leave.
However, retroactive designation is allowed in certain cases:
•    When the employee and employer mutually agree in writing to count the time as FMLA leave.
•    When the employer later learns that paid leave already taken qualifies for FMLA; that period may be retroactively designated if it meets FMLA requirements.
For more information, visit the State of Tennessee Attendance and Leave Manual.