Reviewed by Sasha Božič, Licensed Customs Broker

CBP Form 7501, the entry summary, is the filing that declares how imported goods are classified and valued and how much duty is owed. CBP liquidates the entry from it, so the numbers on the 7501 become the duty you pay unless someone corrects them.
The entry summary and estimated duties are generally due within 10 working days of the goods' release. It is filed electronically through ACE, typically by your customs broker, and it often follows a CBP Form 3461 release filing.
Errors on a filed entry summary can be fixed with a Post-Summary Correction. A PSC can be filed within 300 days of the entry date and no later than 15 days before the entry's scheduled liquidation. After liquidation, the route is a protest on CBP Form 19, due within 180 days of liquidation.
A line classified under the wrong HTS number, a trade preference that was never claimed, or a Chapter 99 duty applied where it doesn't belong all end up on the 7501 as duty paid. Caspian's post-entry audit reads every entry summary line against the tariff schedule and your product data, and flags the ones worth correcting while the PSC window is open.