Liquidation is CBP's final calculation of the duties, taxes, and fees owed on an entry. Before it happens, the entry summary is still a working document and a PSC can correct classification, value, origin, or quantity through ACE. After it happens, the summary hardens into a decision, and decisions are challenged by protest, not edited by correction. The entire choice of remedy is that one status field.
Importers lose money in the gap between liquidation happening and anyone noticing. ACE records the date, brokers receive notices that land in inboxes nobody triages, and the 180 day protest window quietly burns. A weekly ACE report of entries liquidated in the last seven days, owned by a named person, is unglamorous and worth more than most classification software.
A PSC suits genuine errors caught early: a transposed digit in value, the wrong Chapter 99 line for a Section 301 list, an origin code that does not match the commercial invoice. File it with the corrected data and the supporting documents in ACE, and keep the broker's confirmation with the entry file. The correction is part of the record if CBP later questions the entry, which is exactly where you want it.
What a PSC cannot do is rescue an entry that has already liquidated, or substitute for a PSC is not a strategy for a classification position you know CBP disagrees with. That dispute belongs in a ruling request or a protest with the legal argument built properly. Filing serial corrections on a contested position creates a record of an importer who could not settle on an answer, which reads badly everywhere it surfaces.
A protest under 1514 identifies the entry, the decision being challenged, and the legal and factual basis for the importer's position, filed through ACE within the window. The strong protests read like the classification or valuation argument itself: the physical description of the goods, the heading analysis under the General Rules of Interpretation, rulings on comparable merchandise, and the duty calculation that follows if the protest is granted.
Attach evidence at filing, not after a denial. CBP decides on the record in front of it, and a protest that promises documentation later invites a denial that forces the argument into the Court of International Trade, where it could have started stronger. If the protest is denied, that court route exists, but it costs what litigation costs. The filing is your cheapest full hearing. Treat it that way.
Run the clocks on a system: liquidation dates pulled from ACE weekly, protest deadlines set at 150 days rather than 180 to leave drafting room, and PSC candidates reviewed before each liquidation cycle. Brokers will operate this if the service is specified and checked. Left unspecified, most brokerages correct what you send them and protest what you instruct, and the entries nobody looked at liquidate on schedule.
Keep one entry file per shipment with the invoice, packing list, classification worksheet, and every correction and protest attached. When CBP issues a request for information, and eventually it does, the importer who produces a coherent file in a day is practising reasonable care in a form an officer can actually see.
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A post summary correction amends an entry summary before liquidation, through ACE. A protest challenges CBP's decision after liquidation, under 19 USC 1514, and must be filed within 180 days of the liquidation or decision. The entry's liquidation status decides which route exists. Filing the wrong one in the wrong window does not preserve your rights.
On the liquidation date recorded by CBP in ACE, not on the date your team discovers the liquidation. That is why monitoring matters: a weekly pull of newly liquidated entries, with deadlines set well inside 180 days, is the difference between a routine filing and a right that expired unnoticed.
Yes, classification and duty assessment are core protestable matters under 1514. The protest should carry the full argument: the goods' physical description, the heading analysis, comparable rulings, and the corrected duty calculation. Evidence attached at filing matters, because CBP decides on the record presented to it.
The liquidation generally becomes final and the duties stand, with very narrow exceptions. That finality is the reason the protest deadline is treated as the hardest date in the import calendar. If a window has been missed, get customs counsel to check the specific facts before assuming any route remains.