A trustee, creditor, or the United States trustee can ask the bankruptcy court to revoke a Chapter 7 bankruptcy discharge up to one year after the discharge has been granted or the case has been closed.
Section 727(e) of the Bankruptcy Code provides:
The trustee, a creditor, or the United States trustee may request a revocation of a discharge—
(1) under subsection (d)(1) of this section within one year after such discharge is granted; or(2) under subsection (d)(2) or (d)(3) of this section before the later of—(A) one year after the granting of such discharge; and(B) the date the case is closed.