5 C.F.R. § 831.1406
Waiver precluded
(a) When not granted. Waiver of an overpayment cannot be granted when—
(1) The overpayment was obtained by fraud; or
(2) The overpayment was made to an estate.
(a) When not granted. Waiver of an overpayment cannot be granted when—
(1) The overpayment was obtained by fraud; or
(2) The overpayment was made to an estate.