Liquidation is the moment an entry stops being a filing and becomes a final bill. CBP reviews the entry, agrees or changes the rate and value, and assesses the duty. Until liquidation the entry is open and the duty is provisional. After it, the duty is final, and the only way back is a protest or a reliquidation, both on clocks that run fast.
The statute is 19 USC 1504. CBP has one year from the date of entry to liquidate. If it does not, the entry is deemed liquidated at the rate and value the importer declared, which is the outcome every importer quietly hopes for and almost never gets, because CBP's normal cycle runs to about day 314.
The assessment is not a negotiation. CBP checks the classification, the value, the origin, and the trade program, and it changes what is wrong. The importer finds out when the liquidation notice posts, and the notice is the starting gun for every deadline that follows.
CBP can extend liquidation by one year at a time, up to three extensions, with a four-year outer limit. Extensions are routine for entries under review, and an importer who assumes the one-year clock is the real deadline will miss the actual one.
The extension is not a delay tactic. It is CBP taking the time to get the assessment right, and the importer's job during the extension is to keep the records that support the entry, because the questions come at the end of the clock, not the start. Classification is the question that comes up most often at liquidation, and the essential character rule decides it more often than any other.
Before liquidation, a Post-Summary Correction fixes the entry: the code, the value, the origin. It is the cheapest correction in the system, and it is only available while the entry is open.
After liquidation, the route is a protest under 19 USC 1514, filed within 180 days on CBP Form 19. There is also voluntary reliquidation: CBP can reliquidate on its own initiative within 90 days of liquidation under 19 USC 1501, and an importer can ask for it. Accelerated disposition, a protest decided within 30 days, is available when the importer needs the answer fast.
An exclusion that expires changes the duty on entries that have not yet liquidated, which is why the extension date matters as much as the rate. And a low-value entry is not exempt from the clock: low-value entries after de minimis carry the same liquidation rules as any other entry, and the same deadlines.
Liquidation notices post on cbp.gov under 19 CFR 159.9 and stay up for 15 months. The importer who does not check the posting does not know the clock started.
The records to keep are the entry summary, the commercial invoice, the classification analysis, and the payment record, and ACE reports ES-010, ES-701, and ES-702 are the way to watch the liquidation status across entries.
The rule is simple and it is the whole job: check the liquidation posting, calendar the 180 days, and file the protest or the correction before the clock runs out, because a missed deadline is final in a way a wrong classification is not.
The final assessment of an entry, when CBP agrees or changes the rate and value and the duty becomes final. Until liquidation the duty is provisional; after it, the only way back is a protest or reliquidation.
One year from entry under 19 USC 1504, with extensions of one year at a time up to three extensions and a four-year outer limit. If CBP misses the deadline, the entry is deemed liquidated at the declared rate and value.
A Post-Summary Correction fixes an entry before liquidation and is the cheapest correction available. A protest under 19 USC 1514 challenges the assessment after liquidation and must be filed within 180 days on CBP Form 19.
Liquidation notices post on cbp.gov under 19 CFR 159.9 and stay up for 15 months. ACE reports ES-010, ES-701, and ES-702 let you watch liquidation status across entries.