The U.S. Customs Clearance Process at the San Diego Border, Explained

Customs clearance is the sequence of filings, reviews, and payments that a shipment must pass before U.S. Customs and Border Protection (CBP) will legally release it into U.S. commerce. At the San Diego / Otay Mesa border, most freight arrives by truck from Mexico, which changes several details compared with an ocean or air port. The core steps are the same everywhere: file the entry, let CBP review it, clear any exam or hold, pay the duties and fees, and receive release.

This guide walks the process from cargo arrival to release in the order it actually happens, with the paperwork, the government agencies, and the typical timing for each stage. It is written for importers, exporters, and operations managers who want to understand what a customs broker is doing on their behalf and where a shipment can slow down.

What customs clearance means at a land border like Otay Mesa

Clearance is not a single event. It is a set of parallel processes that must all resolve before CBP grants release. On the commercial side, a licensed customs broker files an entry that declares what the goods are, what they are worth, where they were made, and how much duty is owed. On the enforcement side, CBP decides whether to trust that declaration or to inspect the cargo. On the money side, duties and federal fees have to be accounted for. Release is the moment all three converge.

A key distinction at Otay Mesa is mode of transport. Because freight crosses by truck rather than by ocean vessel, some rules that importers associate with ‘customs’ do not apply here. Importer Security Filing, known as ISF or 10+2, is an ocean-only requirement filed at least 24 hours before cargo is laden onto a vessel at the foreign port. Truck shipments across a land border are not subject to ISF. The truck-border equivalent is the electronic manifest (ACE e-Manifest), which the carrier transmits before the driver reaches the crossing.

The Harbor Maintenance Fee (HMF), which many importers expect to see, is also tied to water transport and does not apply to goods trucked across the land border. Knowing which rules attach to which mode prevents both wasted filings and missed obligations.

Step 1: Entry preparation and filing (before the truck reaches the line)

Clearance work starts before the cargo physically arrives. The broker collects the commercial invoice, packing list, and, for Mexican-origin freight, the pedimento and any certificate of origin used to claim USMCA duty-free treatment. From these documents the broker classifies each product under the Harmonized Tariff Schedule (HTS), the 10-digit code that determines the duty rate. Classification is the single most consequential decision in the entry, because it drives duty, admissibility, and which other agencies get involved.

The broker names the importer of record, the party legally responsible for the declaration and the duties, and confirms a customs bond is in place. Any shipment entered as a formal entry, generally one valued over $2,500, requires a bond. Most regular importers carry a continuous bond under activity code 1 (importer or broker), which covers all of their entries for a year rather than paying for a single transaction bond each time.

The entry itself is transmitted electronically through the Automated Commercial Environment (ACE), CBP’s system of record. At a land border the broker also generates a PAPS barcode (Pre-Arrival Processing System) that the carrier attaches to the manifest so CBP can match the truck to the filed entry the moment it arrives. Value tier matters here too: shipments at or under the $800 de minimis threshold can often clear informally under Section 321 with no duty, while goods over $2,500 must go through formal entry.

Step 2: Arrival and CBP review

When the truck reaches the Otay Mesa commercial crossing, the driver presents to CBP at the primary booth. CBP’s system pulls up the pre-filed entry and manifest tied to the PAPS barcode. The officer verifies that the truck, the driver, the carrier, and the declared cargo all match what was filed. This is where good pre-arrival work pays off: a complete, accurate entry can be waved through in minutes.

Behind the scenes, CBP runs the entry against automated targeting rules that weigh the commodity, the country of origin, the importer’s history, and current enforcement priorities. The system returns one of two broad outcomes: the entry is selected for release without inspection, or it is flagged for an exam or a documentary review. A documentary review means CBP wants to see or question the paperwork before deciding, but does not necessarily open the trailer.

If any Partner Government Agency (PGA) has jurisdiction over the goods, that agency’s requirements are checked at this stage. Food, supplements, cosmetics, and medical devices bring in the FDA; agricultural products, meat, and untreated wood packaging bring in the USDA. A PGA hold pauses CBP release until that agency signs off, even when CBP itself has no concern.

Step 3: Exams and holds

If the shipment is selected for inspection, the truck is directed to secondary. The lightest form of exam is non-intrusive imaging, where the trailer passes through a gamma-ray or X-ray scanner (VACIS) so officers can view the load without unloading it. A tailgate exam opens the doors for a quick visual check of the front of the load. The most thorough is an intensive exam, where cargo is offloaded at a Centralized Examination Station (CES) and physically inspected, counted, and sometimes sampled.

Holds fall into two families. Enforcement holds come from CBP targeting, such as intellectual property, valuation, or admissibility concerns. Regulatory holds come from a PGA, such as an FDA hold on a food shipment pending label review or lab results. The importer of record generally bears the cost of exams, including CES handling fees, drayage to and from the station, and any demurrage or driver wait time.

Timing varies widely. A VACIS scan can add under an hour. A tailgate exam typically adds a few hours. An intensive exam at a CES can take one to several business days depending on the station’s backlog and whether lab analysis or a PGA sign-off is required. This is the stage most likely to turn a same-day crossing into a multi-day delay, which is why accurate up-front classification and documentation matters so much.

Step 4: Duties, fees, and payment

Duty is calculated on the entered value using the HTS classification. If the goods qualify for USMCA and the importer holds a valid certification of origin, many products from Mexico enter duty-free, though the entry still has to be filed and the origin claim substantiated. Products that do not qualify pay the tariff rate their HTS code carries.

On top of duty, formal entries owe the Merchandise Processing Fee (MPF), charged at 0.3464% of the entered value with an annually adjusted minimum and maximum per entry. Informal entries pay a lower flat MPF instead of the percentage. The Harbor Maintenance Fee does not apply to truck crossings because it is limited to waterborne cargo, so a typical Otay Mesa entry sees duty plus MPF rather than duty plus MPF plus HMF.

Payment does not have to clear before release. Under CBP’s Periodic Monthly Statement program, an importer’s duties and fees for the month are consolidated and paid by the 15th business day of the following month, which lets cargo move now and settle later. Importers not on a monthly statement pay per entry, generally through the broker’s ACH arrangement. Either way, the bond guarantees CBP that the money will be paid, which is why the bond has to be in place before the goods can be released.

Step 5: Release and after release

Release is CBP’s authorization for the goods to leave the port and enter U.S. commerce. For a clean truck entry with no exam and no PGA hold, release can happen at or shortly after the primary booth, and the driver continues to the delivery point. When there has been an exam or hold, release follows once the exam clears and any PGA has given its sign-off.

Release is not the end of the customs cycle. The entry summary, which finalizes the classification, value, and duty owed, is filed and the duties are deposited, on the periodic monthly statement for importers enrolled in that program. CBP then has up to 314 days from the filing date to liquidate the entry, the point at which the duty calculation becomes final. Until liquidation, CBP can issue a request for information (CBP Form 28) or a notice of proposed action, and the importer can correct errors through a post-summary correction or protest.

Recordkeeping obligations continue well past delivery. Importers are required to keep entry records for five years from the date of entry. This is why the accuracy of the original classification and valuation matters long after the truck has crossed: the declaration you made at Otay Mesa is the declaration CBP can audit years later.