19 CFR § 173.2 - Transactions which may be reviewed and corrected.
The Center director may review transactions for correctness, and take appropriate action under his general authority to correct errors, including those in appraisement where appropriate, at the time of:
(a) Liquidation of an entry;
(b) Voluntary reliquidation completed within 90 days after liquidation;
(c) Voluntary correction of an exaction within 90 days after the exaction was made;
(d) Reliquidation made pursuant to a valid protest covering the particular merchandise as to which a change is in order; or
(e) Modification, pursuant to a valid protest, of a transaction or decision which is neither a liquidation or reliquidation.